Those are simple calibration sheets with numbers for top and bottom layer tests.
I made those to calibrate filament and printer for speed and line width for the top and bottom layers to see which ones are the best for quality.
You can also test Ironing settings if you need.
Just import models to Prusa Slicer and set printing by objects, add desired modifications to each model like speed, line width or ironing settings to compare the best results.
The size of one sheet is 20mm x 20 mm x 0.6mm so It has 3 layers of 0.2mm.
Numbers can help you find which one was which when slicing.
It can mean speed in mm/s or flow etc.
The author marked this model as their own original creation.