Hehe, I noticed it as well. I think it’s meant to say 12.7 x 99mm, which seems to fit that caliber shown in the belt. Funnily enough 2.7mm is a real cartridge made for the tiny 2mm Kolibri pistol.
The 50 BMG is measured differently in some countries. A good rule of thumb is if it looks like it would be the little brother to the 20mm anti tank/ material rilfe round then it is the 50 BMG / .50cal
If you look at the gun, the box on the side that has the coil on the top going into the gun is probably just meant to be for the robot. Without the box would probably be the actual gun. I think.
So .50 BMG is a 12.7mm cartridge and 12.7x99mm is the official Swedish size for the weapon Automatgevär 90 or Barret M82A1 as it is also called. Swedish ammo