Can someone explain highscores?

[Insane n00b]

Deeply confused, might be just being a noob.
Dark Lust is #1 with 3mill xp.
Yet it's 12 mill xp for a 99.. and there's people with 99 thieving? Wat
Edit: Oh, is it based on level, not xp?

 

[kill dank]

Total level, yes. XP is irrelevant.

 

Total level is what they're ranked by answered.