Circuit Breaker limit definition question

I have read and understood what is curcuit breaker. But the meaning of the curcuit breaker settings such as is still unclear to me. Is this a limit of estimated memory usage of a single incoming query, or it's the limit of the current memory usage plus the estimated memory usage of the incoming query?

The total circuit breaker wraps the request and fielddata circuit breakers to ensure that the combination of the two doesn’t use more than 70% of the heap by default.

It's the incoming request and also the existing (fielddata) cache.

Thanks but that's not what I was asking. I meant:
indices.breaker.fielddata.limit = existing field data memory + estimated new field data memory requirement
indices.breaker.fielddata.limit = estimated new field data memory requirement

This one.

OK, thanks!