There's a featured lists and autofill feature built into the game. That's what you are seeing when your squad is automatically filled. A total 14-19 members work to pull the squad to the featured lists that you see on the right tab, but they must be active. If you have 20 or more squad members, your team can enter the autofill feature. Your squad needs to be active and you need to set the medal count requirement to zero and open to all. You will fill up in a short time and can remove players you don't want. The key is keeping your squad count in either the 14-19 range or 20+ for autofill. Even if they are inactive, I would keep the player if that will push you below 20. The autofill is the fastest way to get players, and you just need to remove one or two at a time, and keep the process going. Stay above the minimum thresholds to stay on the radar for new players. Give yourself some cushion, since players do leave.
Squad Level: 50