This dialog is available from the Options / Fonts... menu command under the Graphs window.
This dialog allows you to customize the fonts used for displaying text on the graphs. The font being set depends upon the current number of displays set. There is a different font memorized by Fund Manager for each one, four, or nine number of displays. This will allow you to make smaller fonts when the number of displays is higher, and larger fonts for easier viewing, when the number of displays is smaller.
Fonts are memorized in portfolios. If portfolios are not being used the most recently set font for each display is used upon startup.