The size you have quoted is the tyre size, which helps a little, but not completely. If these are genuine Audi wheels, they should have the correct centrebore 57.1mm, but as you say you can fit spigot rings to get over that. The PCD needs to be 5 x112, that's the number of holes for wheel bolts the diameter of the circle that passes through the holes. If the ET really is 15, then they are going to stick outside the wheelarch, way too far. The normal ET is 51.