Minecraft, chest with arrow turns up, meaning?

Day!

I do not remember exactly how long I've been playing Minecraft, but I guess it'll take a few years. (Minecraft PE, on the phone) And I've noticed many times, that while playing from time to time such a chest on the top right of the screen with a top-down arrow, pointing to the chest, appears. Today it was a few times again, and I just do not understand what it means.

Can someone help me there?

This means that the game will be saved if it crashes. So that's just the car memory in the settings you can make it synonymous

that makes NO SENSE