Concerning F,F&S...

Greetings!
I recently picked up Fire, Fusion & Steel and it's GREAT!
I'm trying to write a program from windows through it, but I have
one question (for now).  How are the numbers on the Hull Size tables
determined?  I can figure out the relationship between tonnage and
volume, but the rest of it confuses me.  Any ideas?

Lucifer >:} 'tis good to be back...