In the Rulers dialog, you can set ClarisDraw to "Use Fractions When Appropriate" when displaying lengths in an autosize line. If you draw an autosize line, then resize it a few times, it may revert to decimal display. For example, instead of displaying an autosize line as 15' 2", it displays 15.17'. The workaround is to select the autosize line, then, in the Object Info window, retype the length in feet and inches. This will reset the autosize display to feet and inches. If you resize the line further, it may revert to a decimal display again, requiring the same workaround.
Test conditions:
Tested ClarisDraw 1.0v1 and 1.0v2
Ruler settings of 8" = 30ft and .25" = 1ft tested, 12 divisions per foot
Drew horizontal autosize lines
Resized with shift key down to attempt to constrain to horizontal. Resized both larger and smaller about 2 - 10 times until the issue occurred
Hardware: Quadra 800/7.1 w/System Update 3.0