I set up an surface slope label expression which took the absolute value of the slope, then used that expression in a slope label style. When I created the expression, I incorrectly formatted the result as double rather than percent. When I change the format of the expression from double to percent in my drawing, the labels display correctly; however, if I close and reopen the drawing, the expression defaults back to double format, and the labels do not display correctly (until setting the expression back to percent).