It’s not a case of being loved - Chapter 2

I was re-reading this and just noticed something.
In the first chapter, MC says she only has two stones left to find and it showed some panels of the stones she has already acquired. It was three stones that she had. So the first chapter implied there were five stones. But in this chapter, it shows that there are SIX stones.
I can’t tell if the writer genuinely forgot or didn’t even plan it and just wrote something new here.
It’s not important to the story overall but it seems like an oversight.