This happened to me today. Had three tickets on hold that were supposed to total 69,000 miles, and the actual price came in at 83,000 when I went to purchase. A quick call to the EXP line resolved this with no argument on their end.

The only reason I even noticed was that I incorrectly entered one of the digits from my credit card. This forced me to repeat the payment, and my attention fell on the fact that this was not the right number of miles. Kind of annoying