Change to output beam 2 in this widget, the (data) index selection widget.
Then click on "Calibrate". After this, select output beam 3. When you calibrate
triple amplitude data, the output beam selection is irrelevant. Run "Calibrate"
on these data just once.
Remember, in the calibration widgets you select how to calibrate the data and which calibrators to use, and in the plot and index selections widgets you select which data to apply the calibration coefficients to.