Strange bug, system restore

I had system restore activated for a long time.
Windows 7 64 bit.
One day i noticed that my os partition was very full. 10gb “disappeared”.
I found out that system restore was set to 50%. More than what was left on that partition.

I erased the points. And set it to few percents.
This gets reset automatically after a while. To 50% again.
Then i disabled system restore completely for the os partition. The other partition restores were disabled allready. And nothing gets saved there.

But the os partition STILL saves. Even if its disabled! And allways resets to 50%.

What is that? It shouldnt save anything if its disabled?

Good bye avast