The amount shown is your fixed balance + your income from the current round combined (might be great btw. to have a different colour for the fixed balance in that graph too!)
I like this. I'll try to make this happen soon.
In the meantime, the stats main page has been improved : there's a hashing power graph and a list of recently found blocks.
Check it out here !Edit: done. I had to reset the individual graphes, but this time should be the last.