In Krastorio 2 it has a second tier of beacons called Singularity beacon.
It accepts 2 modules, but its effect transmission efficiency is 0.75 and not 0.5, so the calculator shows lower numbers than in reality.

Probably code should read beacon transmission efficiency data so it takes it into account :)

I'm not sure you posted for the correct mod. Module Inserter doesn't calculate anything regarding efficiency. All it cares about is the number of module slots and restrictions regarding productivity modules.

Hot damn, sorry, I was meaning Max Rate Calculator... :\ Was late at night....

Haha, no problem :D