Here's how I interpret the G-code you posted (my comments added to code). Let me know if this makes sense....
G92 E0 ; zero the extruder at current position
G1 E1.1 F360 ; extrude 1.1 mm filament --- this is the RETURN from the previous retraction, which would be two lines before the G92 E0 line...
G2 X87.591 Y109.894 I12.409 J15.106 E6.6594 F1182 ; move X/Y and extrude 5.5594 mm filament --- this is laying down filament, going from the 1.1000 above to 6.6594, thus 5.5594 mm
G1 E5.5594 F1200 ; extrude -1.1 mm of filament --- this is moving the filament from +6.6594 to +5.5594, thus -1.1000 mm
G0 X87.661 Y109.965 F18000 ; we retracted the filament, now do the X/Y rapid
G92 E0 ; zero the extruder. Next step will be to extrude 1.1 mm to RETURN from the retract two lines up...
I think they have it right. And if we put in an offset for return from retraction, it would be added to the G1 E... F360 line.