well if you look at the cover art...
So there will be like 7 of them
At least, that's 7 that we know of from the cover art. There could easily be more added just because they can, lol
Or maybe there were always more planned, but they could only reasonably put 7 on the same page
I mean, the first three are definitely the first three on the front, in order
But the idol doesn't quite look like a back view of them would match the fourth. . .
Maybe the fifth? But to be fair we can't see a lot of them just from the top of their head
And on top of that, in chapter 2 the charm says Yuu prayed for another meeting with Karin
excessively for ten years
On the page explaining that alone Yuu said Karin's name at least ten times as well
Ten seems to be a rather interesting number for that chapter, at least