IF THE ORIENTATION OF THE AXIS LIKE SHOWN IN THE FIGURE THEN MX REPRESENTS THE VERTICAL MOMENT AND MY HORIZONTAL AM I RIGHT OR WRONG PLEASE CORRECT ME.
You may refer this. Please also refer help file to know in details.
file:///C:/Program%20Files/Bentley/Engineering/STAAD.Pro%20CONNECT%20Edition/Help/GUID-777CEFB1-4F20-457A-8594-C3F8288A1AF5.html