Hi Olivia,
I see that you are maybe watching the clock a bit too much. The times in EASY are recommened times and if he naps 15 mins less one day it's ok. Depending on their day, how much activity, milestones, teething, growth spurts and so on they're sleep will fluctuate. This is also true during transitions between 3.5 and 4 hour EASY.
During days 12-16 you do extend the Atime by 15, but then have a 1.5 hour nap. I know this seems like a step backwards but it's just to get the one less feed established. Does that make sense?
Once those days have gone by you go back to 2 hour naps.
Unfortunately the best guide we have is the one on page 230
The only thing that gets shorter and remains shorter is the E time as they become more experienced eaters
.
HTH
-Beca
P.S. Try to read his cues more than the clock, it helps to stop obssessing about the clock and following what your ds is telling you.