if its fine at the front but not at the back then the issue is with your bed levelling not the offset.
This is the macro I use for levelling my bed on my ender 3
M671 x29:198:29:198 y35:35:204:204 P0.5 ; The location of the four bed securing screws
G28 Z ; Home Z
M558 F240
G30 P0 X29 Y35 Z-99999 ; probe near an adjusting screw ; Front left screw
G30 P1 X198 Y35 Z-99999 ; probe near an adjusting screw ; Front right screw
G30 P2 X29 Y204 Z-99999 ; probe near an adjusting screw ; Rear left screw
G30 P3 X198 Y204 Z-99999 S4 ; probe near an adjusting screw ; Rear right screw
G28 Z ; Home Z
Run this and it will tell you how much each corner needs adjusting.
