Why would 16 people unfollow is a very serious question and I understand where you're coming from but those could be random accounts that followed him and then later got suspended or blocked or de-activated. There could be a million reasons so it would be very difficult to just see those numbers and figure if it's real or not, you would have to dig deeper into analyzing and each followers using different metrics which is a very time consuming and resource consuming process.
Also, if it's taking so long to figure it out, how does it even matter anyway, as long as the account is getting good attraction and engagement, I believe it works well for the user.