Adding stabilizer

Is it possible to dissolve stabilizer too fast? I put 7 lbs in two socks and had the kids "play with them" in front of the skimmers. It was all dissolved by the end of the afternoon. My CYA reading was at 20 and I was trying to get it to 60 per my SWG system recommendations. 8 days later I got a reading of 40 but my pool store said it was 20. They want me to add 7 more lbs. but I don't want to get it too high. They said I dissolved it too quickly and that I should have let it hang in front of the skimmer and dissolve on it's own. I have an 18x36 IG SWG pool with a vinyl liner and I'm having trouble keeping my chlorine level up.

Dissolved is dissolved. The speed at which it dissolves can't change the amount that is now in the water. What kind of kit are you testing with? If you are doing the disappearing black dot test, I'd trust your own reading. You are right in that you don't want it too high.