Thought I better return the comments
car's looking good Claire, the multifit is to do with the stud pattern, i.e. 8 holes in the wheel and you turn the wheel to line up with the holes in the cars hubs.
Bill is talking about offset which is how far out/ in the wheel sits in comparison to the wheel arch the lower the number after "ET" is the further out it sticks. My OEM ET35 wheels will sit out further than Cupra ET38 ones.
Hope that's of some use to you