offset moves the rim IN not OUT.
LESS offset would move the wheel further from the car and give you more width. However, it also moves the center line of the rim which adversely effects the suspension.
If, say, 6" was as wide as I could go on +53 and I wanted to put a 8" rim on there without doing anything but moving offset, you would move the offset 1" (25mm) to +28. The 8" rim would be in exactly the same position relative to the fender well but would simply stick out further by 2"
2015 STi: Still Stock
04 STi, 04 WRX: SOLD