Resource capacity evaluation

Dear SNP and PP experts,

I am trying to sink in the criteria for evaluating resource capacity as explained in help.sap.com. I read it thrice but I am unable to absorb it in my little mind why such an elaborate criteria for evaluating resource capacity ?

I shall much appreciate if someone can kindly explain in simple words or direct me some internet resource/ expert blog if one exists (couldn't land one incl on resp. sdn forum wikis) that explains the SAP's intentened logic of capacity evaluation of resource when there are multiple capacity variants, capacity profiles, reference resources

I somehow managed to visualize a telescopic nature of 'search' criteria (as is common in several other programs in SAP) but I could not gather the science behind this cryptic capacity evaluation logic. I would resist at this point of time to conclude that it could have been simpler.

Also please help understand why do we need a capacity profile when there are 99 capacity variants possible !

Many Thanks

Guru