Which numbers are YouTube's, and which VideoCore calculates
Two kinds of number sit in every panel. YouTube's own live stats, and the rates and ranks VideoCore calculates from them. The panel says which is which, every time.
Live stats, from YouTube
Views, likes, comments, subscribers, age, length and tag count are YouTube's own public numbers, read as they are.
Rates and rank, calculated by VideoCore
Views an hour, engagement, like rate, views per subscriber and the rank are VideoCore's arithmetic on those numbers, and the block is labelled so.
The same line on every page
The free health check says it under the title: the grade and every score on this page are calculated by VideoCore from public YouTube numbers, not a YouTube metric.
Why it works this way
Every number VideoCore calculates says so under it: calculated from public YouTube numbers, not a YouTube metric. You always know whether you are looking at a fact from YouTube or a calculation from us.