Now that is something I never knew before...looks well useful, too; I think it's the amount of stuff that's rendered in your view or maybe in that portion of the map that's being rendered, such as the amount of triangles on the faces and the textures, texture memory etc. Looks like Romania takes up a lot of texture memory...can't see it very well but it looks like the red stuff says 69mb

And you have 1 pixel shader
Similar to showbudget in Source, just generally for seeing if maps need to be improved for rendering purposes.