According to those specs it’s 31khz. Just need to select the appropriate monitor settings when setting up Groovymame in Video Mode Maker so that GroovyMame will know to not go below 31khz. You probably will want to add some scan line effects to more closely mimic a 15khz screen. It will work fine and for some games that were 31khz resolution you’ll have a native picture.
If you have an existing GroovyMame computer setup, and it’s outputting 15khz your monitor will most likely give you an “out of range” pop up assuming the Windows desktop was setup at 15khz. You’d have to boot into safe mode and change that to a 31khz (VGA, 640x480p) setting to get a picture on that monitor, and go from there.