I cannot teach our UR5e loading allowance from stick-out alone

I watched two setters load our spacer blanks by hand and write the exposed lengths on the same sheet. The numbers varied, and the discussion immediately became how much the robot should compensate. Nobody measured each blank's overall length against those entries. I want a better exercise before that idea gets into the UR5e plan. What should we pair on each identified blank so the learners can see whether the blank itself differs or the seating differs? Automatic loading is still outside this trial.