When they can carve the score in stone before hand it seems likely that old assertions that the games were rigged and the destined losers (captives) to be killed may have been accurate.
My guess is that the outside rim figures are numbers and that some kind of pointer was used to indicate the score. Similar to their calendar.
Since it is a circle, there must have been a ‘Top Score’ to achieve a win, like ‘21’ in basketball or in Tennis................