Solution to the problem concerning the object to be 3D printed is off center in Printrun (Pronterface)

I ran into a problem while switching from Kisslicer to Slic3r (slic3r-mswin-x86-1-2-9a-stable) to print the Twisted Spiral Vase on one of my Prusa i3 3D printer. The problem is that, no matter how I try, the object to be 3D printed always appear on the bottom left corner (see below photo).

Here is the setting for my Pronterface.

After couple hours of trial and error, here are my findings and solution to the problem.

In Slic3r, when the origin of the print bed is set to the center - in this case, X: 90, Y: 100 (see below photo) and the setting is written into the configuration file, the bed shape setting in the configuration file is "bed_shape = -90x-100,90x-100,90x100,-90x100" (see the next photo).

When the origin of the print bed is set to the bottom left corner - in this case, X: 0, Y: 0 (see below photo), the bed shape setting in the configuration file is "bed_shape = 0x0,180x0,180x200,0x200 (see the next photo).

Note,
1. Simply changing the X & Y values in the Bed Shape window and clicking the save button under "Printer Setting" won't write the setting into the configuration file. To write the new setting into the configuration file, select "Export Config.." under the File pull down menu.

2. The "Export G-code.." command can be performed immediately after the X & Y values in the Bed Shape window are changed and the Gcode generated will be based on the latest X & Y values.

With the origin set to X: 0, Y: 0 in Slic3r, the sliced model is now placed in the center of the print bed (see below photo).

It's worth to note that in Kisslicer, if the object is to be placed in the center of the print bed, the configuration is like the one shown in the red box in the photo below.

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For the Twisted Spiral Vase, here are the settings in my Slic3r configuration file (config_18x20_PETG_E3D_160323.ini).

# generated by Slic3r 1.2.9 on Thu Mar 24 09:37:45 2016
avoid_crossing_perimeters = 0
bed_shape = 0x0,180x0,180x200,0x200
bed_temperature = 0
before_layer_gcode =
bottom_solid_layers = 3
bridge_acceleration = 0
bridge_fan_speed = 100
bridge_flow_ratio = 1
bridge_speed = 60
brim_width = 0
complete_objects = 0
cooling = 1
default_acceleration = 0
disable_fan_first_layers = 3
dont_support_bridges = 1
duplicate_distance = 6
end_gcode = M104 S0 ; turn off temperature\nG28 X0  ; home X axis\nG28 Y0  ; home Y axis\nM84     ; disable motors\n
external_fill_pattern = rectilinear
external_perimeter_extrusion_width = 0
external_perimeter_speed = 50%
external_perimeters_first = 0
extra_perimeters = 1
extruder_clearance_height = 20
extruder_clearance_radius = 20
extruder_offset = 0x0
extrusion_axis = E
extrusion_multiplier = 1
extrusion_width = 0
fan_always_on = 0
fan_below_layer_time = 60
filament_colour = #FFFFFF
filament_diameter = 2.93
fill_angle = 45
fill_density = 0%
fill_pattern = honeycomb
first_layer_acceleration = 0
first_layer_bed_temperature = 0
first_layer_extrusion_width = 200%
first_layer_height = 0.35
first_layer_speed = 30
first_layer_temperature = 165
gap_fill_speed = 20
gcode_arcs = 0
gcode_comments = 0
gcode_flavor = reprap
infill_acceleration = 0
infill_every_layers = 1
infill_extruder = 1
infill_extrusion_width = 0
infill_first = 0
infill_only_where_needed = 0
infill_overlap = 15%
infill_speed = 80
interface_shells = 0
layer_gcode =
layer_height = 0.3
max_fan_speed = 100
max_print_speed = 80
max_volumetric_speed = 0
min_fan_speed = 35
min_print_speed = 10
min_skirt_length = 0
notes =
nozzle_diameter = 0.4
octoprint_apikey =
octoprint_host =
only_retract_when_crossing_perimeters = 1
ooze_prevention = 0
output_filename_format = [input_filename_base].gcode
overhangs = 1
perimeter_acceleration = 0
perimeter_extruder = 1
perimeter_extrusion_width = 0
perimeter_speed = 60
perimeters = 1
post_process =
pressure_advance = 0
raft_layers = 0
resolution = 0
retract_before_travel = 2
retract_layer_change = 0
retract_length = 2
retract_length_toolchange = 10
retract_lift = 0
retract_restart_extra = 0
retract_restart_extra_toolchange = 0
retract_speed = 40
seam_position = aligned
skirt_distance = 6
skirt_height = 1
skirts = 1
slowdown_below_layer_time = 5
small_perimeter_speed = 15
solid_infill_below_area = 70
solid_infill_every_layers = 0
solid_infill_extruder = 1
solid_infill_extrusion_width = 0
solid_infill_speed = 20
spiral_vase = 1
standby_temperature_delta = -5
start_gcode = \n
support_material = 0
support_material_angle = 0
support_material_contact_distance = 0.2
support_material_enforce_layers = 0
support_material_extruder = 1
support_material_extrusion_width = 0
support_material_interface_extruder = 1
support_material_interface_layers = 3
support_material_interface_spacing = 0
support_material_interface_speed = 100%
support_material_pattern = pillars
support_material_spacing = 2.5
support_material_speed = 60
support_material_threshold = 0
temperature = 165
thin_walls = 1
threads = 2
toolchange_gcode =
top_infill_extrusion_width = 0
top_solid_infill_speed = 15
top_solid_layers = 0
travel_speed = 130
use_firmware_retraction = 0
use_relative_e_distances = 0
use_volumetric_e = 0
vibration_limit = 0
wipe = 0
xy_size_compensation = 0
z_offset = 0