1. Is the 54 Inches the wall height or water level? Your pool may hold 15,000 gallons but 24' round x 4' deep is only 13,500 gallons.
2. What is your chlorine source? What is the strength and age and size of container?
2a. According to Poolmath, 1 gallon of fresh 12.5% LC will raise 15,000 gallons water by over 8 ppm FC. 1 jug of fresh 8.25% bleach will raise FC 5.3 ppm.
2b. At 13,500, a gallon of 12.5% will raise yourwater by over 9 ppm FC. 1 jug of fresh 8.25% bleach will raise FC 6 ppm.
3. How are you testing? You should be continually swirling the water as you add drops and you shouldn't be leaving more than a few seconds between drops. The solution will turn pink again before too long. That is why more than few people hear love them their SpeedStir. I happen not to have one, but what I've found is that I can keep the vile on the table and swirl it like a glass of red wine with my dominant hand. Then add drops with my off hand.
All that said, yes, you should go through quite a few jugs on day one. Did you get the color change?