Newbie who lacks pool smarts needs those who have The Smarts

[Pool Dorkus Maximus]

Yup, that's my pool! My 20x20, 38,000 gal pool . Oops. I measured last night using the 'step it off' method, except it's quite clear that I didn't understand it; when I entered last night's numbers, I thought wth? bc I knew they seemed bizarre. Thanks so much for helping me out on it. My poor, poor pool is in challenged hands.

Anyway....I followed Watermom's advice and added 5 gal of 6% last night....which I thought might bring me up to the 25ppm suggested. Here are this morning's numbers:

--chl: 7ppm
--alk: 180
--pH: 7.6
--cya: 150
--no visible signs of any algae; water clear

I'm really confused as to why it only went up to 7ppm, after 5gal...any advice on what I might try next? Should I use actual Shock powder this time, would that be easier until I get it to a better place? For longer term, how will I get that cya down permanently so that the chlorine is better managed? I may be asking all the wrong questions, but I sure hope to learn.

Thanks again!