The difference between this ET40 and factory ET52 is basically going to see the rim’s lip moving 12mm closer to your fender (52-40). In other words, the rim’s lip moving 1.2cm closer to your fender, or, about half an inch closer to your fender. You can go check yourself by putting your finger between the rim and the fender. Good to go.
And if you’re eyeballing this with your finger, consider that unless you’re SURE sure that you have factory rims (or unless you’ve seen the offset stamped on the back of the rim), then you might just have replicas with a different offset than OEM. Or, you may have aftermarket wheels with Frankenstein’d center caps that just look factory. Again, offset might be different on aftermarket wheels that look factory. If you see any pictures of my wagon on here, then those wheels are not factory. They just look factory (factory Audi front of cap stuck on aftermarket caps).