Filotto's coverage gate only counts words you have proved

Filotto keeps several tiers of evidence about a word. Some are strong: you answered it, or you marked it known on the calibration grid. One is a statistical inference from a recognition checklist, useful for placing a learner and weaker than it looks. The chapter generator had to say, in code, which tier the shipping gate measures against.

Both candidates were run against a volume already read and judged. The generous boundary scored it at 99.4 percent, comfortably easy. The narrow one scored it at 95.5 percent, and its reader had said that chapter read harder than usual. The generous gate would have called a chapter too easy on the evening its reader called it hard.

So coverage counts proved words only. A statistical inference about two thousand words is not two thousand words of comprehension.