A4 B8 Wheel sizes?
 

I am looking to build a set-up for winter and on checking the Tirerack, there seems to be varying offsets listed:

17" = +35, 40, +45, +48

18" = 35, +35, 40, 45, +45

Please shed some light on the many different sizes that fit the same car.

What is the Original Audi wheel's offset?

Cheers.

A4 B8 Wheel sizes?
 

Are these machined to 66.6mm to make them fit on the B8s, or are manufactured from day one as 66.6mm? if they are machined, are they fully approved and tested for all load bearing, TUV, DOT, etc etc etc.???