This is apparently something that the investigators picked up from a CFI, copied, and then redacted unrelated personally identifiable information (all the black-out) before posting. I always keep descriptive logbook records of what I've done with students, with corresponding notations placed in the student's log, and sometimes formal lesson summaries and check-off lists that correspond to progress along a syllabus (typcially for basic instruction, but generally not for fight reviews, aircraft check outs, etc. for licensed pilots). I don't keep a calendar as shown, and I can't tell from this if it is the only record that particular CFI would keep (I would hope not). It does not appear to reflect any standard practice I've encountered, so I'm hoping it's a supplement that the investigators found interesting or useful for some purpose in their inquiry.