Can someone translate that for us so we understand? We all are not fluent in latin.
So, you can look up a quick translation in your Missal of the part that begins "Indulgentiam, absolutionem ..." after the Confiteor, at least the first one.
In brief, in the one after the first Confieteor, the priest says the equivalent of "may God forgive US OUR sins" (brief paraphrase)
OP says that his priest changed it to "may God forgive YOU YOUR sins" (again brief paraphrase), but then SimpleMan and I are thinking he heard the "YOU YOUR" in the SECOND Confiteor, not the first one. If you look at the contexts of both, it does in fact make sense to use US/OUR the first time, because the priest also says the Confiteor, but then in the second one, he does not say it, and he's already received Holy Communion at that point, so it makes no sense to say "US / OUR" at that point.
If OP did hear a priest who said "US / OUR" in the second one for a long time and then recently heard him change it to "YOU / YOUR", it could be that he had simply reiterated the first one without thinking about it, and then at some point he gave it some thought and realized he should change it to "YOU / YOUR'. This is possible since the second one is informal and not actually in a lot of Missals.