If I understood Rob correctly, it is based on the number of block found in the pool the last 7 days, but if you did not found any block it check your submitted shares.
I want to add this:
I have 100% boinc utilizzation.
If i solo mine and find 1 block in one week, i gain 150grc.
If i pool mine and find 1 block in one week, how many grc i gain? I suppose << 150...am i right?
If it's so, what's the reason to use the pool?