233 kit - CYA test question

I've had the 233 kit for a couple of years and just noticed something about the CYA test.

The instructions on the box say to first fill the mixing bottle to the 15ml mark with pool water. The instructions on the mixing bottle itself say to first fill the bottle to the 15 ml mark with CYA reagant.

The mark doesn't look like it's halfway up the bottle, so I'm thinking it matters. Which is correct?

Thanks. :)

I just follow what it says on the bottle. :)

Michael