NYC electrical code 408.60(E)(4) and (5)

[Tainted]

408.60(E)(4) and (5) talks about sizing the through (main) bus and section bus. The code section can be found here:

https://www.nyc.gov/assets/buildings/pdf/ll39of2011_electrical_code.pdf

How exactly do I perform this calculation? is this calculation my responsibility or the manufacturer's responsibility?

For example if I have (6)-600 amp disconnect switches fed by a through bus, does this mean the minimum rating of the switchboard needs to be:

6 x 600 amps x 70% = 2520 amp rated switchboard required

 

[infinity]

I think that this would fall on the switchboard manufacturer and wouldn't be the concern of the designer.

 

[Tainted]

I think that this would fall on the switchboard manufacturer and wouldn't be the concern of the designer.

Here's what I also don't understand, when we for example tell the manufacturer that we want a 3000 amp switchboard,

is the 3000 amps the through bus rating? How does the manufacturer make the calculation based on the parameters we provide them?