I am new to doing residential design and have gotten confused by the optional calculations in the back of the NEC for sizing the service of a dwelling unit. I am used to sizing the service by getting the load in amps and then multiplying by 125% and selecting the next standard size. It looks like the optional calculations allow you to get the load from 220.82 and then just round up to the next size for the service. Is this correct? Are they considering the load the calculations to be non-continuous and therefore the service size doesn't need to be 125% increased? Thanks for your help.