Many of the values in the config file are measurements of lengths. The following units are valid: `"In"`, `"Cm"`, `"Mm"`, `"Pt"`, `"Em"`. *However*, there are many cases in which `"Em"` is not valid. This is because many of the lengths need to be converted to Pts and there's no easy way to do what with Ems because they're font-specific. I recommend using Em for values only where `example_talmudifier.json` uses Em.