Walking as a Low Aerobic Activity

My 945 LTE shows that I am overdoing High Aerobic and underdoing Low Aerobic. I tried walking quickly for half an hour as a Walk activity. I stayed mostly in Zone 1 but with some Zone 2. There was no change in my Low Aerobic 7-day load; it stayed at 103. Does Walking contribute, or just Running, Cycling and Swimming. If it does, about how much walking would add at least one point?