It seems to me that the base font size is larger than we specify. I was able to reproduce by going to the advanced settings and changing the minimum font size. If the user has done that, they're effectively altering your layout, and it's up to them to tweak the settings until it works.
It might also be some weird Chrome or Windows 10 font sizing issue, but I can't find any info on that.
(Click to enlarge)
#1848 - Small template displaying issue on iMac
It might also be some weird Chrome or Windows 10 font sizing issue, but I can't find any info on that.