Anyone knows about units for exchanging in Mistplay?

When I installed the game a bit over a month ago, the number if units to exchange for a $25 Amazon card was 5500. When I reached that and went to exchange it had increased to 5700, I exchanged anyways ... A couple of days later it showed 5500 again and 1100 to exchange $50. I am at 9700 now and it shows 11400 to exchange $50. Anyone else having the same experience?