If you have an Onan Quiet Diesel 7.5 or 8 kw generator these do not put out 240 volts. These are actually producing two 120 volt legs of power through a large inverter. If you were to try to measure between L1 and L2 you would read zero volts. This is because they are in the same phase of a sine wave. Your shore power coming into the coach is however 120/240 volt and so your EMS will show exactly what you are seing and it is correct. On generator power the amperage at the top of the EMS is the total being used.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7