I know that if a user is removed, all his votes will be cancelled. So some users may have negative reputation changes as a multiple of
5. But How
-2 reputation change for user removal? I got this message few minuets before. Any idea?
The rep change reported for removed users is the total effect. You don't know how many actions are involved in that. So if you've been reasonably active yourself -- have lots of posts that could be voted on, have accepted answers, have edited, etc -- then just about any number is possible. No breakdown is available.