The Read Manager works on what Read nodes you have selected. It lets you manipulate the frame range, the before and after frame options, the ability to frame hold on a specific frame, and what to do when it finds a missing frame. This is especially helpful when you’re rendering on 10’s or 20’s, since you can then set your full frame range in the Read node and then just tell it to go to the “Nearest Frame” when it hits that gap for example.