Aloha jojo14,
The "lines," or "ticks," between the numbers are in degrees of two. It is implied on the first bullet point on page 12 of the Level one course where it walks you through using a compass.
the .5's are just in reference to where the different directions,(or i-ching reading in the hexagram course)stop.
As simram mentions, you wont need this level of specificity in the Level I and II course, but knowing you have a half degree buffer in the Level three course can come in handy.
Much Love,
Shawn