% of FGA by Distance

[GeorgeMarcus]

So basketball reference provides some very useful "% of FGA by distance" metrics, where they break it out into 0-3ft, 3-10ft, 10-16ft, 16ft-3pt, and 3pt. I'm conducting some research related to these statistics, and I was hoping somebody could help me out...

A) Is there any rhyme or reason as to why they broke it up the way they did? 3pt is pretty obvious, so I'm really asking about the other 4 tiers.
B) Is there anywhere I can look up a more specific breakdown, so that I can calculate % of FGA from 0-5ft instead of 0-3ft?

Thanks in advance