Titan League Points Strangeness

[calmon]

I play Titan League (1.121 points) and actually won 7-8 games against Zero_killer (1.487 points).

Now I lose a game against him and I wonder:

The last 2 games I won (and can check) I got:

Calmon! +15 / Zero_killer -10
Calmon! +15 / Zero_killer -10

The one I lost:
Zero_killer +22 / Calmon! -15

If I remember correct I got in all won games against Zero_killer never more than 20 points.

Why is there such a difference in points? I think Zero_killer is pointwise one of (or the) highest players in outwitters. Why do I lose more for a loss and get less when I win? All games was given up. Any ideas?