First thing to know is that the mA output module can be set via secondary settings only for volts, amps and power. So using the CT and PT ratio, we need to convert to secondary the MW value that you desire. 50 MW is equal to 50,000,000 / (1600/5 x 14400/120) = 1302 w. Therefore, the high value (20 mA) = +1302 w while low value (4 mA) = -1302 w.
To set the meter, using Communicator EXT > Device profile > Ext I/O module > Assign each output to Watt Total