(Num)  If specified, causes the font for the control to be scaled by the specified percentage (100=100%). This factor is applied in addition to the global font scale factor found in the Misc. Settings menu, so should only be used to adjust the font size of a particular control relative to the others.

Note that what is being scaled in this case is the point size of the font, and that may not correspond linearly to what you might expect. For example, if you want to create a static text control with double-high characters, and have specified coordinates with erow = srow + 1, you may find that a fontscale factor of 200 is bigger than you want. (Or it might fit the height but be too wide.) Some experimentation is in order here, and it is also highly recommended to be conservative (i.e. go for something smaller than the maximum size that will fit), because different resolution screens and other display parameters outside of your application’s control may affect the sizing. (It is better for a message to be slightly smaller than you wanted, than for it to be so big that it does not fit, or wraps inappropriately.)