Samatha,
3 loaders is the default value. I haven't found where it is but you can change the default, but you can on EACH target you are loading.
click on the Target Table, change the "Number of Loaders". In this example I changed from default to 10.
I use this rul for the number of loaders ... equal to 1/2 the number of CPU cores, then up it by 2.
So if the cores were 16 ... my value is 10.
Hope that helps.
Mike