Clan points.

Why do I get sometimes Negative Clan points? Example:

Date: Points_Before Changed Points After
2011-01-28 446 -23 423
2011-01-28 402 44 446
2011-01-27 358 44 402

I know if I get 500xp I get 1 clan point. And max. per day is 10clanpoints = 5000xp.
I get everyday 5000xp to get 10clanpoints and so do my clanmates.( try )
No1 didn't leave my clan yesterday, I got like 6 players in clan so idk how it has gone to Negative. + We won 7/8 of our clan wars.

And here is my clan for incase: http://clan.z8games.com/clanstat_cf.aspx?guildid=136877