Currently, we aim to print with the same point size as the font is shown on screen. This is not necessarily the same physical size as on screen, since JavaFX prints with 72 DPI and many monitors now have 90 DPI (not to mention HiDPI adjustments). This means that the font size can appear a bit bigger than it does on screen.
The best solution to this issue is to ask the user for a font size when printing, with a sensible default. This could be in the existing print options dialog when printing all classes, and in a new input dialog when printing a single class.