Yes, that is a great count for betting decisions. But keep in mind that count doesn't yield very good decisions for your stiff hand decisions, which are pretty important in this game.
In BJ your 12v2,3,4 and 13v2 are pretty much the only important ones, but in this game you need to know 13v4,5,6 ; 14v2,3,4,5,6 ; 15v2, and all the bonus hands (such as 7,8 vs 3 which is at a TC of about 0). So in those decisions counting the ace as -2 kills you a bit. Not too much but just keep that in mind.