the clamp meter doesn't provide bench trst readings but rather the amount of amprage being drawn through the power line into the amp in which case it is above 10 or 20 amps which is usally the max. a multimeter can handle
basically what that will tell you is amprage in, then you can determine how many volts are out through the speaker outputs, from that you can find out exactly how many watts your amp is putting out and also how efficient it is