What is this? (Fuel glitch)

It is a simple mistake to restart the page and everything is normal image image


It’s a visual bug.
It happens when 1 fuel is given while you play a mission.
Upon mission completion,the fuel would show as +2 instead of the +1 you got during the mission,this extra one being a “clone” that disappears after the next mission played (if not another fuel recharges,then it happens again).
It does not affect the gameplay whatsoever and you don’t lose anything either.

How do you make those things so huge…