Really? Are you 'guesstimating' that? (There's no marking for "10" on the K2006).

If that is so, you need to be using dichlor to chlorinate. The fact that there WAS 6 ppm FC when you tested, doesn't mean that it won't be ZERO an hour later, if the sun comes out!

The SS recipe page (link in my blue signature block) will cover much of the info you need.