It's a portuguese (brazilian portuguese) word, which it means like a joke/prank without any reason to be done, just like someone who pranks on a online game, like killing a guy for no reason, or exploding and shooting everyone just for fun, it's a prank/joke for people, but for brazilians it's a "zueira", or making something just to show or to make fun, like passing a red light for fun, for brazilians it's a "zueira", or simply making a joke, for brazilians it's a...

the thing that you don’t have when you’re phones percentage is over 20

A prank, a joke. "Zueira" can also be a lie, just to make fun of someone.