Facebook like out of nowhere?

I’ve created a site that I haven’t shared with anyone beside a secret group on facebook (composed of 3 members including me). When I installed the facebook like button on my site, the count indicated 5… only us 3 know the existence of the page.
Today this happened again, I posted the link again in the group and got two other likes. I was wondering, does posting link increase the likes count? I’m pretty sure my partners didn’t share the site with anyone.

Edit: it seems that everytime I post the link in the fb group, that counts as a like… didn’t know that

that might explain why there are always more likes than +1 on some sites