Scott, that is not mal-positioned egg clear in the point after day 16 is no an extra "air cell", there is fluid in the point of the egg, it will take time to absorb that fluid. and it can still hatch, just don't think about popping open that egg. ( I found some of my eggs also have clear in the point day 18, but lock down begins 3 days before the hatch, 18,19,20,21 so that is 4 days, we are jumping the gun just a bit...
Good news is you have a few days yet for the egg to absorb, give that egg more time than normal.