Using 1999 NEC,does the second sentence of 373-6(a) mean if you have conductors in parallel you have to combine them first then use Table 373-6(a)?
For instance, 2-500Kcmil's in parallel are figured as a 1000Kcmil and a minimum 10" gutter width is required?
But if the same 2-500Kcmil are not in parallel only a 6" gutter width is required?
Why don't they fill in the multiple wires per terminal column on 1000Kcmil and larger?

This is concerning question #11 of the calculations section from the IAEI study guide Plan Review in case anyone has it.