On the certificate of my January Psychology A exam I got 68. I converted that with the UMS converter which equals out to 100 UMS points and I've seen on AQA's grade boundary chart that you need a 55 for an A. Well I got 68 and received a B. Is that right?
When you say you got 68, that would have been your UMS score. Hence, you should have used the grade boundaries the other way to calculate your raw mark. If the UMS was out of 100 (which I suspect it was) then 68 is a high B.
Perhaps 68 in raw marks would have been 100% UMS, but the score you receive on results day IS the UMS mark.