there is a bug that causes my 5s display to go into extra large font size

Hello, edapplebaum.

Thank you for visiting Apple Support Communities.

With iOS 7 you can adjust the displayed font size to a desired size via the steps in the first article below. We also do include several other features such as Zoom, Larger and Bold Text options in Accessibility that can be adjusted. Check out the second attached article for more information regarding these features.

iOS: Adjusting the font

http://support.apple.com/kb/HT5956

iOS: Configuring accessibility features

http://support.apple.com/kb/HT5018

Cheers,

Jason H.

You may have Zoom on... double tap with three fingers to turn it off. Then, go into Settings > General > Accessibility to disable it.

See p. 138...http://manuals.info.apple.com/en_US/iphone_user_guide.pdf