The green arrow indicates the line belongs to you.

The two individuals in the front are the ones who are defending the line. In a combat match, you and another comapny member will share a line to earn season points. Between both individuals, the one with more damage will earn the extra season points.

Anyone crit attacks on your line can only be blocked by the two individuals who own the line with their shields. Any company members doing more damage than the two individuals who own the line will not impact where the rewards go to.