I have a GE zoneline AC/heater unit 230/208. going on a double pole 30 amp breaker. is 10-3 to small should go 8-3
If you look at the top right hand part of the label in your picture it shows that there are three different heat strips that go into this unit. The largest requires a 30A breaker for protection, but to be able to answer your question you need to contact the seller and see if they have the information on which heat strip is actually installed, or you can contact GE Appliances and see if the serial or model number can tell you what size the heat strip is.