Quest log interface help

Hi i just have one question about the quest log

when you open the quest log, to the left of the completed quests, what's that tiny little bar mean?

It appears for me on some acts/diffs and not on others

I'm assuming this means I'm missing quests or have them all completed but i can't tell which or if that's even what it means

Do you mean the scrollbar on the bottom?

EDIT: Disregard, I apparently can't read this early in the morning.