I want to address a few things-
#1 - the pool store would have likely told you that your pool is fine & you were good to go after it looked “clearish” & blue because they don’t concern themselves with fully eradicating algae or proving so with an accurate overnight chlorine loss test. Make no mistake, they would have still sold you something

(no telling what).
#2 you have a 19k gallon pool, it takes anywhere from a 1/2 gallon to a full gallon of 10% liquid chlorine to replenish the average daily fc loss of 2-5ppm in your climate when you’re not doing the slam process. So Your usage during the slam is not extreme especially considering your low cya.
#3 the
SLAM Process with its 3 exit criteria including the
Overnight Chlorine Loss Test are designed to be the most efficient & effective way to eliminate algae & prove its gone whilst still being safe for surfaces, equipment, & swimmers.
*For the slam - testing & replenishing fc is imperative, the less you test & replenish the longer the whole thing takes since you end up at less effective fc levels for longer periods.
The more often you do it, the faster it goes. Especially in the beginning when consumption is higher.
It’s often recommended to begin slam on the weekend (or when you have a couple days off) so you can aim for dosing every couple hours & get a leg up. As fc demand slows so can you, down to 3 times a day or so.
*For the oclt -
it is not a valid measurement of loss if you don’t do
both tests in the absence of the sun
Or
you don’t actually test
After your last fc addition & just assume you achieved your target.
This is extremely important as the 1ppm loss threshold leaves little wiggle room.
I think you might have actually passed the oclt much sooner had you been doing it exactly as the article says.
#4
PoolMath & logs
I understand if you prefer paper logs, many do.
That said, it is extremely difficult for others to decipher your written notes.
If you don’t wanna use poolmath for keeping logs (which is definitely worth the $7/yr btw) you can click my avatar & see my logs
Perhaps creating a standardized log sheet would be clearer in the future.
Also using the resulting ppm instead of /alongside drops & cups makes it much easier to follow especially if asking for assistance & trying to make out patterns.
You’re on the other side now so be sure to keep it that way by following the appropriate
FC/CYA Levels - setting your swg to maintain high target

is good insurance incase of a higher uv day or other variables. Your swg brand & size isn’t listed in your signature so I can’t really offer guidance on run times or %. Please update that along with your filter info.
You can however use poolmath effects of adding (in the hamburger menu) to determine what it takes for your particular swg to create 3ppm/day and start there. Select swg then the

to select your swg
View attachment 488093