Those figures on those websites are a good guide, but all babies are different. My second DS has always slept heaps more than "average" (and still does), while DS1 has always had less than "average". The best thing to do is to be in tune with Jazz - if she seems tired all the time she might need more sleep. Otherwise she is probably getting just the right amount. And as you have noticed, at that age they don't have long "awake" periods. So it is not unusual for them to show tired signs within an hour of waking up (both my DSs used to have their first nap just 1/2 an hour after waking up from their night sleep). It does get easier to read the signs as you go. You are doing a top job so far, just trust your instincts.