Yep... the way it is now is correct but does have the problem of dropping out of the top 100 on levels like 64. At least this means you only have to play once 100 other people (or teams) have done so. Of course once 100 people get the same score it's only worth about 85 points so it not so much of an issue (as two people dropping your 1000 points to 500 without much/an effort).
It's a pity about the ticks on old versions and I'd still suggest that if DREAM had replayed his "old levels" he'd be ranked number one. I think it was a good idea to bite the bullet and change it. Every now and again an old player comes back and betters their score. Having said that it's probably more refreshing for people to go for new scores rather than chase their old ticks. Their problem.
Is good as is :)
Oh, and this is why I don't have a "number one count". It's hard to handle the case where people are tied (ie the query wouldn't be that efficient.