If you have a list that you are starting with I can see how the number might be flexible. You aren't sure exactly how many teams you are considering. Maybe you get info on a team that makes you think you should consider them. Maybe you get info and think a team is now out of the running.
But once you narrow the list, you have a list. A solid concrete list of teams that you are comparing, contrasting, and considering. The list is 6 teams. Or 7. Or 8. But at this point it sure as heck is not 6-8.