So the spacers are to compensate for the offset, right?

The spacers are similar to the 5 lug adapters, but don't change the bolt pattern or number of lugs. They are designed to allow the use of commonly available 4-4.5 FWD wheels (a la Honda) on older RWD cars.

And also for the backspacing if not wrong I think the offset is 0.

You can see how they look.

Its a photoshop work (the size can change; make that using my eye measuring system).