He is not counting Belgrade among his ranking points at the moment, but only Chennai and Casablanca. If you look at his page, http://www.atpworldtour.com/Tennis/P...inka.aspx?t=rb
, you see that Belgrade is among his "non countable tournaments".
If next year, when Chennai points will come off, Waw won't have a better 250/CH-results among his tournaments, Belgrade points will be added (*)
(*) that, of course, not considering the new rule about the possibility (under certain circumstances) to replace the worst 500-results with a non-countable tournament at the end of the year.