This is something that bugs me since the release of the current interface. I always thought that someone will notice it and fix it but seems like no one cares.

1. Go to the PLAY tab
2. Click on FIND A CO-OP BOT MATCH
3. Pay attention to the 3 boxes in the main window (especially the DIFFICULTY box at the right)
4. Now switch to a different side tab e.g. Find A MATCH (keep looking at the right box)
5. Realize that the box size changed a little bit.

I know you will call me crazy but this bugs me like hell.