What is the meaning of the number in the upper-right corner of the Watchtower screen?

I'm wonderig how to interpret the number and color. Watchtower shows a score of 1141, the color ranges from green to blue and the 'arrow' is at 12 o'clock. I could only guess that colors like orange and red are some kind of warning and green or blue are good.

Just a suggestion. Switching back and forth in Watchtower the score is animated every time even if nothing has changed. I would prefer some kind of caching, i. e. animate only if something has changed or after some time has passed.