It shows low level, when your level is below the level that the team set for applicants to join.
Especially the high ranking teams require a high level to join.
The team leader can set the minimum level to enter. And he/she decides if the team is open (everybody over the minimum level can join) or invitation only (you need the minimum level to apply, and then need a confirmation from the team leader.)
The level we are talking about is your level in the game. The number appearing on the golden star on top in your camp.
