Your bin edges don't match up exactly with those numbers so there will be data in the starting and ending bins that are outside of the range you want. Therefore you can't do it from the histogram directly. You must count the values of Af that lie in the range. Here is how you do it:
count1 = sum(Af >= 0 & Af <= 0.05)
count2 = sum(Af >= 0.05 & Af <= 0.1)
count3 = sum(Af >= 0.1 & Af <= 0.15)
