Progress is counted in customers, not images. A customer is complete only when every
usable image of that person carries an accepted stage — a complete series per person is what the
progression model will need.
Images
Labellers
corrected = the verifier kept the photo but changed the stage — the labeller graded it wrong.
A plain accept/reject count misses those, because a corrected label still counts as accepted.
wrong % is (corrected + rejected) / checked, and only means anything once a verifier has looked.