What is the Difference between Breast Base Width (BBW) and Breast Width Diameter (BWD) (photo)

I am 2 weeks post op (got round gel mentor overs) and really happy with them so far however would have liked to go bigger as the swelling is almost gone and have already dropped in place. The Surgeon said i couldnt go bigger then 250cc (high profile - implant diameter 10.5cm) due to the width of my chest. Here is a copy of my chart from the consultation. I just want to get some other opinions to see if this is right? Have attached a photo too from the other day if it makes any difference.