They track your workflow: a page starts as Draft, becomes Transcribed once the model has run, and you set it to Finalised once you've proofread it, using the status control in the transcription panel. Each page in the column of pictures carries a mark: nothing for Draft, a document glyph for Transcribed, and a circled tick for Finalised. Occasionally a mark fails to update after an automatic retry; the transcription is there when you click in, and you can set the status manually.
