How to calculate the estimated size (estimated_size) of "Parent Circuit Breaker

Currently, _nodes/stats are in the state attached below.
As it is, it is caught in the limit of Parent Ciruit Breaker, which causes a Circuit Break.
I would like to know how to deal with this.

I am aware that the Parent Circuit Breaker is the total value of each breaker.
Currently, the total value of request, fielddata, in_flight_requests, and accounting is 【about 7gb】. However, the "Parent Circuit Breaker" has a different value of 【15.1gb】.

What elements other than request, fielddata, in_flight_requests, and accounting are included in Parent's estimated_size?
And how can the other elements be checked?

"breakers": {
    "request": {
        "limit_size_in_bytes": 13480335769,
        "limit_size": "12.5gb",
        "estimated_size_in_bytes": 0,
        "estimated_size": "0b",
        "overhead": 1.0, "tripped": 0
    },
    "fielddata": {
        "limit_size_in_bytes": 5777286758,
        "limit_size": "5.3gb",
        "estimated_size_in_bytes": 5602323384,
        "estimated_size": "5.2gb",
        "overhead": 1.03,
        "tripped": 4991478
    },
    "in_flight_requests": {
        "limit_size_in_bytes": 19257622528,
        "limit_size": "17.9gb",
        "estimated_size_in_bytes": 5013,
        "estimated_size": "4.8kb",
        "overhead": 2.0,
        "tripped": 0
    },
    "accounting": {
        "limit_size_in_bytes": 19257622528,
        "limit_size": "17.9gb",
        "estimated_size_in_bytes": 1422893443,
        "estimated_size": "1.3gb",
        "overhead": 1.0,
        "tripped": 0
    },
    "parent": {
        "limit_size_in_bytes": 18294741401,
        "limit_size": "17gb",
        "estimated_size_in_bytes": 16292575432,
        "estimated_size": "15.1gb",
        "overhead": 1.0,
        "tripped": 2
    }
}

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