that is normal and expected. the problem comes when one retreats again and still has the same ammonia. Prime also locks up oxygen so eventually the fish can suffocate.I have a 10g gallon tank running empty (no fish) for few months now. To keep it cycled I add 8 drops of pure ammonia (Old Country) every few days or when I remember. By the next day, all ammonia is gone. I don't check NO2 or NO3 but change water weekly.
Today I took a sample from this tank to make sure ammonia is 0. I added 8 drops ammonia like usual and took a sample. I added 20 drops (1 ml) "locker" Prime and took another sample. Checked ammonia in both and guess what? Same 4 ppm reading, no difference.
Locked or unlocked, ammonia is there.
Prime works for cloramines as well (often found in city water) by breaking them into ammonia and chlorine. Chlorine is then split into chloride and ammonia, well, locked into a complex for about 24-48 hours. For the amount of chloramines found in city water, 2 drops of Prime per gallon seems effective. But 4 ppm ammonia is no match for Prime at regular dose.
Meanwhile the locked ammonia is much safer then the free ammonia. So there is a difference. In this case prime locked up some or all the ammonia. Just the tests don't reveal that fact.