I know I'm late to this, but you can press left to start adding 10 gold at once, left again to deposit 100, left again 1000, etc. This way you can control exactly how many coins you want to deposit!
Alternatively, you can just press right as soon as you enter the deposit screen, to start depositing 100 million coins at once, so you can deposit all of your money with just 3 presses! Right, up, confirm!