If the baby's admit date is less than their first occurance date, in column J, then they were possibly in with the mother when they were first born, not needing to be in the NICU. Does this make sense? An example of this is Pt Nbr (column B) is 2452590. As you can see, their first day in the NICU was 1/11/13, but baby was born on 1/9/13. So, in this instance, I would want to count the baby as an admit on the 1/11/13 day only, even though the baby stayed in the NICU for 48 days.