Hmmm... several questions come to mind:
Did you see your ammonia and nitrites levels go up, and then come back down to zero? Are you using RO
water, or tap?
Since you're showing nitrates, I'm *assuming* that your ammonia/nitrites spiked and you're looking at the end of the cycle. But if your ammonia/nitrites did NOT ever go up, and you have nitrates in your source water to start with, then you may have not even started the cycle.
To answer your question though... the nitrates are not going to magically disappear right away and you'll have to do water changes to get those numbers down as low as possible. As the tank matures, and under the right conditions, denitrifiing bacteria will convert the nitrates to nitrogen gas... but you've got a while before that happens.