VGG-16 confusion

Can anyone explain me why in the VGG-16 architecture goes from a 224x224x3 to a 224x224x64
after applying 2 conv 64 with 3x3 filter, s=1, same?
if i use week1 formula the next size would be (224-3)/1 +1=222. i was expecting 222X222X64
Nh=[(Nh+2p-f)/s +1] same for w
please help

got it p=(f-1)/2