No. Your understanding is based on a team's record with respect to a hypothetical situation where they, instead, won 50% of their games. The real meaning is based on a team's actual wins with respect to their actual losses.
My understanding was based on the simple math (the only kind of math I'm any good at, BTW
) of figuring out how many more games than half (.500) a team has actually won. That's really it. Since half of 10 is 5, I figured a team with a 10-0 record had won 5 more games than half, and was therefore 5 games over half, or .500.
There was nothing hypothetical or conditional about my understanding, though. When I was saying "they are 5 games over .500" I was saying "they have won 5 more than half of their games." When most people say "they are 5 games over .500" they are saying "the team would need to lose their next five games in order to have won half of their games at that point."
My understanding was simply describing what has happened. As I've already conceded, my understanding was mistaken, in that the accepted usage defines "over" as "away from", not "more than". But it is the common usage of the term that is filled with conditionals and hypotheticals, not mine.