Since after 8 minutes it wasn't cooked enough he put it in for more time. So that means the arrow should be pointing to more time. But the circle isn't filled in because it is more than 8 minutes.
So.. in this case, the starting amount is the 500mg sample... and the rate of decay, negative rate, is 1%, and at the time, the elapsed days is 0, to t = 0, P = 400
