API (and salifert and maybe others) nitrate test converts nitrate to small amount of nitrite and then measures that converted nitrite.
The consequence of this is that if you still have any nitrite in the water it will convert to a huge nitrate reading when using the nitrate tests, the conversion factor is big, 20-50 for different test kits.
Do not test nitrate until your nitrites are clear blue 0. At the moment you most likely have zero nitrates and when nitrite goes down and gets converted to nitrate you will have around ~10 nitrates.
Then you can do a minor water change and go.
p.s: search Reef2Reef for exact tests, but I just cycled 3 tanks and confirmed that this is true. Also 1ppm ammonia is converted to 2.6ppm nitrite and 3.6ppm nitrate and as your cycle look quite "clean" you can only have ~10 nitrates at the end.
