Game output not taking up full window

When launching the game output, the text inside only fills up half the space vertically (even less if I try to resize the window larger). Unsure of how to recreate this bug, but I originally discovered it while running optifine, however I can confirm it is occurring on my vanilla profiles as well.

 

Unsure what the version numbers at the top mean. This is happening for me in 1.16.4 and 1.16.5.