What does ‘Instagrammer’ mean in Instagram DM?

Instagrammer in DM

So today…

While I was scrolling through my feeds, in what felt like that I should arrange a get together this summer with all my ex-school mates.

Clicking the DM arrow, I wasted not even a single second to send an invitation message in the group that I created years ago.

But wait!!!

I realized that many of my friends have either made a new account after school while the others deleted it.

Post-clicking the info button on the top of the group, I rushed to check the number of users who were still a part.

And I see what?

Instagrammer!

…