Here's a quick run-down:

• Members of the pack (once it's defined) are outlined in white
• Blockers who are in the engagement zone, but NOT members of the pack are outlined in red
• Blockers who are out of play are outlined in gray
• The centre of a given dot represents "the hips" for the purposes of distance measurement
• The outer edges of a dot indicate in/out of bounds. If a blocker is overlapping the edge of the track, they are "straddling", if they are totally out, they are "out" (each looks slightly different)
• The big ugly green lines indicate "Pack is Here"
• The text in the centre of the track summarizes what's going on