RCB30B2B is the model number of a condenser unit. For the tonnage, you need to check which air handler you got inside. My guess is that it's a 3 ton blower.
But as far as RCB30B2B - the picture below is an excerpt from Amana's Service Manual which explains the model number coding.
So, RCB30B2B would translate into Remote unit, Cooling System Type, 10 SEER efficiency, 30,000 BTU Nominal Capacity, 2-nd marketing series, 230V/60Hz/1phase power, 2-nd design series (modified once).