SEVENTEEN has 13 members. Not 17. Stop asking.
13 members + 3 units + 1 team = 17 (SEVENTEEN)

Honestly, I wasn’t really into K-pop that much.
But as I kept listening to music, I thought, “Wait, this is SEVENTEEN?”
I just kept playing their songs, and then I got curious and looked into them more.

I hope what I’ve gathered helps you too.