Am on my phone so can't google but there are tables that show how many hours an average baby sleeps at each age. My DS (8mo) has never slept 'enough' in the day according to all the books but his ideal sleep at night is 13 hours, therefore it adds up to the total. (He still wakes for feeds at night about 50% of the time). If your DD is grumpy, maybe try a slightly earlier bedtime, but sounds fantastic to me! DS didn't manage anything even approaching that until 6mo!