Unclear labels "H Desktops" and "V Desktops"

My father couldn't understand that the V and H Desktop sliders are used to change the number of virtual desktops, even though he was looking for exactly that functionality.

He has basic English reading skills, but he's not a native speaker (and there is no Italian localisation). However, his first understanding of H and V is hight and velocity (from physics). A more explicit labelling would be helpful, maybe a parent "Number of desktops" label, and "horizontal" or "vertical" on each slider.