You are right that CYA takes up to a week to dissolve and you are also right that you may end up needing to add a little more. In your pool, 4 lbs. should add about 20ppm of CYA.
For the next week or so, you'll probably need to add some bleach morning and evening. Once your CYA is up some, you should be able to test and dose in the evenings only.
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