In case you are curious what this means, they are trying to cut back on the number of fake accounts and followers that people purchase or have spamming them. This doesn't mean you've done anything wrong on your account, so there is no need to worry.
I didn't see any drop in my followers today, I have had quite a few new followers today though, nearly 200 already! All real. :-)
Did you get the message on your Instagram? Let me know in the comments below!