What happens when you mount a larger bore opening to a smaller center bore?

[Zoich]

So I bought those style 214 wheels today. After everything was said and done, I found out this was a take off set from an X6. Let me rewind. So the owner had 19in for his X6's when he first bought his X6. Then bought this set. But really wanted go even bigger, so he only mounted these wheels on for like a week. I checked the part number of the wheels and they matched for the X5's front & rear (rear especially).
Learning from previous postings, it was said that X6s have smaller rear center bore at 72.5mm. So it looked like he mounted the X5 rear wheels (part# 36 11 6772250 matched in the pic) on to his smaller center bore.

Just out of curiosity, since the difference is so small 1.5 mm (so 0.75 mm radius), how bad is it is to drive like that? looks like he needed a hubcentric 0.75 mm hubcentric ring for his car to fit properly which he didn't do? do they even make rings that small?