Ask a new mother how many hours she slept and she will do arithmetic. Two, then one and a half, then maybe forty minutes. The total is five and a quarter. It is also useless, because five hours in one piece and five hours in four pieces are different nights.
The shape of a night
The check-in asks about sleep in blocks, the way it actually happened. The longest stretch matters more than the sum. Two decent blocks read differently from six fragments, and the score treats them differently.
Why this matters to the score
Sleep is one of the signals that weighs most in the Refuel Score. If it were a plain total, a fragmented night would look fine on paper and the score would be wrong exactly when it needs to be right.
Apple Health can help
If she wears a watch, sleep can be read from Apple Health so there is nothing to type. Nothing is written back and the import can be turned off.
The point is not to measure the night. It is to know what today has to work with.