Some people did not submit their development hours at the end of the month, which means they can wait until the USD/GRC price drops before getting paid in GRC, meaning they get more GRC. (Though I'm not certain if this is factored into how Rob released funds).

Another way to handle this problem is to pay according the average GRC price over the last month. Also another way - though this may be controversial - is to set standardized payments in GRC, not USD - this would also give us a better sense of when funds are expected to run out. That being said, I think the most important opinions on that latter proposal are of the devs.