For your 7000 gallon pool, 19oz of CYA assumes starting with 0 CYA. If the tube is cloudy, but you can see the black dot at the 30 mark, then the CYA is between 0 and 30. Maybe assume a starting point of 15-20 CYA, target 30 and add that amount of CYA so you don't overshoot.
Another...