Chick pipping

So I’m really new to this but yesterday morning I noticed one of my 8 eggs started pipping. Today coming up in 24 hours in a few minutes I’m not sure if the progress it has made is normal? I don’t see any sign of a zip just pieces of shell broke off and a small tear in the membrane. Any info of advice would be much appreciated. I will attach a pic I took at 8 am yesterday morning and one I just now took and post. Thanks in advance. It’s day 21 and this is the only one pipping so far but I hear chirping and see the other eggs moving frequently yesterday.