This came up elsewhere and I am just curious about what the answer is.

If someone has a main service panel with a 200-amp main breaker, how many
amps of service can that panel actually service?

I am probably not wording this correctly, but I thought that I remember
something about a 200-amp main breaker actually being okay for 400 amps of
service since there are two separate circuits coming in (a 240-volt service
split into two 120-volt circuits in the panel box).