offset is the distance from the center of the wheel to where the wheel hits the hub of the car..

0 offset means 1/2 is on the inside of the hub, and 1/2 is outside the hub..

+ (whatever) offset means 1/2 the wheel + (whatever) amount is on the inside of the hub..

you probably wont run into - offsets with fwd.

it is measures from bead seat to bead seat, not lip to lip. EX: a 7 inch rims is typically closer to 8 inch if measured lip to lip..