Hi, and welcome to the community! Congrats on the eggs. Here is a website that has an excellent explanation.
www.beautyofbirds.com/cockatielshatching.html
Also, if you cannot get the info with that URL, then search as follows:
Beauty of birds. Hatching cockatiel chicks and their first days of development.
It says 18-21 days, until hatch, but you are very close to it. To me, pipping means actually breaking the shell so, your babies should be doing that soon. And you will also hear the babies peeping in the shell!
Good luck! We will welcome updates!
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