PPM = Parts per million.
You could do a 50% water change and still get the same reading of ammonia. Did you know that?
The higher your ammonia is, the easier/faster it is to get rid of it.
What you're aiming for is to remove as much as you can with water changes and hope/wait for the bacteria to consume the rest to retrieve the 0 ppm ammonia reading you want!
Also, did you know that Ammonia is more toxic/lethal at higher temperatures?
I posted the following on my blog a while back:
1. Ammonia gets more toxic at higher pH levels
2. Ammonia toxicity is significantly influenced by temperature and pH. The lower the temperature and pH the more ammonia can be tolerated.
3. Lethal ammonia concentrations at a pH of 6.5 are 0.73 ppm, while at pH 8.5 only 0.17 ppm are considered lethal to inhabitants.
4. A fish tank kept at 68 degrees F can tolerate more then twice the amount of ammonia as a tank kept at 86 degrees F.
5. Nitrite levels should be at an undetectable level at all times after the tank has fully cycled.
6. Detecting nitrites often means that the biological filter is not working properly, or the tank is overpopulated and the filter can not handle the load efficiently.
Lets hope your bio filter takes care of that.