I'm building a watch face using Garmin's Connect IQ API. The watch face is designed for running so I want it to be easily readable. I'm looking for a font for numbers that covers roughly half of the screen. I am trying to avoid creating a custom font because I need to keep the storage to a minimum.
They list the font sizes with descriptions in the link below.
https://developer.garmin.com/connect-iq/user-experience-guide/page-layout/
Size 17 seems to be the largest size and it claims to cover the entire screen. On my device, the height/width of the font is approximately 1/5 of the screen height/width. Can I manually adjust the size or am I stuck creating a custom font?
The system fonts/sizes available are fixed and all that is available without the use of a custom font; you cannot manually adjust the sizes of any system fonts.
The descriptions given in the UX Guide are more "in general" as the fonts vary from device to device. The "Thai Hot" size for the system number font is listed as covering "most of the screen" not the entire screen but that was probably more true with the CIQ 1.x devices (Fenix 3, FR230, etc).
Using a custom font isn't that hard -- there are some good tips in this blog post -- and isn't necessarily memory intensive if you are selective about what characters you include.