Good. The 0 ammonia means that you've developed enough bacteria to convert the 4-5ppm of ammonia you're dosing daily. Now, it's a different bacteria that converts the nitrIte, and you're just waiting for them to catch up to what the first type of bacteria can do, then you're done.
Keep feeding the ammonia so that those bacteria don't starve to death waiting on the others.
Also, your NO3
measurements are likely unrealistic, as IME high 'trites will cause that test to not read accurately. It's good to see if they're moving or not, but don't be surprised if it holds at 20ish, then the day your 'trIte drops to 0 they jump up to 40. Mine just did that to me a few days ago, and every tank I've cycled has acted that way.