Not sure what size the bases are in the Bambu Handy app. It would be helpful to add the diameter in mm to the build plate names. Or in the description.
In Bambu Studio the plates are labeled according to size. I will investigate the Bambu Handy app.
Update: I just checked in Bambu Handy and all 8 plates on both 3mf files lists the names. These follow, generally, the standard sizes from D&D, Gargantuan = 4 inches squared, Huge = 3 inches sq., Large = 2 sqin, Medium = 1 inch. The Small is about .75 in and the tiny is about .5 inch.