A games score is a very simplistic way of measuring how many weeks a game was in the top 10 list and how high it the list it ranked.  A game is given 10 points for ranking #1 in a top 10 list, 9 point for being number 2, and so on down to 1 point for ranking #10.

In other words, games accumulate more score for each time they appear in the top 10 list and a higher appearance in the list is worth more than a lower appearance.