Clearly you're in the USA and 115 volt territory.
20 Amp will be fine - 1000 Amp OK too if you could make it fit - 10 Amp - what the switch would be here in Europe - no good at all - far too puny.
The rating of the switch - 20 Amp - says how much current is can take without stress.
There will be a rating plate somewhere on your machine that shows the Power Consumption - Wattage. just divide the Watts by 115 Volts to get the approximate current the device is likely to take.
Good Luck..., August 2015