i’m guessing you are talking about these on both sides.
in multiplayer, these would be used for, well, multiplayer reasons. the left side shows how much garbage you are about to receive. so here, there’s a red line 4 blocks tall in the left thing, and when i receive that garbage i get 4 lines of garbage.
the right side can be used for something else. one example would be to indicate level or lines cleared. so if cleared 7 lines out of the 10 lines needed to advance to speed level 2, the right side would be 70% full.
so those 2 columns are there in case i need them at a later time, and if they don’t need to be used, they won’t be.