I agree Chemgeek, it is not worth trying to figure out. As I stated, that pool and its issues are long gone. However, there are 3 facts to consider.

1, Multiple vanishing black dot tests were performed at 3 different pool stores, and I'm sorry but I can't believe ALL of the tests were faulty tests. In all total, at least 6 different test were performed (2 per store). I asked each of the people performing the tests to be very careful with their testing. My CYA was over 100, way over.

2, High CYA readings (over 100) are reportedly difficult to read unless you do a little fancy dilution with distilled water, which none of the pool stores did.

3, I bought a 6 Lb. bottle and took the remaining unused CYA back to the pool store and had it weighed. with the bottle, there was 2.1 Lbs of unused CYA left over out of the original 6 Lbs. So I can say it with a pretty high degree of accuracy that 4 Lbs. was all I put in.