Most of it's usually unused, too. Progressions should be obvious. Total weight in lbs. WSR minus 15. Ignore it for now.
Positive encumbrance gets a character points.
Negative encumbrance costs points. Use the WSR column and read across to get Light encumbrance. Use the method you prefer, and mark the appropriate Medium, Heavy etc. That's enough to put him at Medium encumbrance. ST x 2.4, so using the Carried Weight column again gives Neg 1 encumbrance.