If you're in a team that has a 700-day Veteran or Lifetime Subscriber in it, they have a special ability that gives 5% more Skill Points and Bridge Officer skill points to all members in their team when Skill Points are earned.
This is why if you're in a group that doesn't have a Lifetime Subscriber/minimum 700-day Veteran, you won't see this pop up.
Well, if you saw a 700 day pop up for you, you were probably doing a team-based event with a player who was a 700 day (or more) Veteran. In turn, this gave the team a 5% skill point bonus for each player. So basically, for every kill in the match, you got 5% more skill points for it, with a bare minimum of an extra 1 skill point at a time I think.