It is more an interpretation issue. I believe if you have seen other in one battle mission you are used to already seeing the number below.
You only need to go to Tier 4 your can free exp up to Tier 4 very easy and cheap.
Play to win eventually you can probably get the 3 kills.
You can do it on random. I also recommend inviting 2 friends to help. Think about it, the flank you are in will be mostly your friends. You can TEAMWORK to lower the HP and you can take the last shot.