The Font Scaling parameter in the Dialog Sizing dialog is equivalent to the Proportional Font Scaling option on the Misc Settings dialog, except that the form applies only to dialogs, whereas the latter applies only to the main window. Also, the scaling basis is somewhat different between the two. In both cases, 0 indicates the standard Windows font size (i.e. no scaling). Any other percent value for the Font Scaling factor in the Dialog Sizing dialog is relative to that same standard Windows default font size. So 100% in this case is equivalent to 0; 125% would give you fonts that are 25% larger than the standard Windows default font. (In contrast, the font scaling factor on the Misc. Settings dialog is relative to the size of the main window grid.)

For dialogs using the Windows desktop font size grid, increasing the font scale factor also increases the size of the grid units and thus increases the size of the dialog and all the controls within it. The overall effect is similar to what happens when you change your Windows desktop font DPI, except that here the effect is only limited to A-Shell dialogs. In contrast, for dialogs using the A-Shell main window grid, changing the font scaling factor does not affect the size of the dialog; it only affects the size of the text, and the height of combo box controls. (If the Misc Settings option to force edit box height to match the combo box height is set, then changing the font scale factor also changes the edit box height.)