You need to identify how many of each instance there are of each type and then multiply with either 1 or 0.5. The sumproduct function can do that for you (
https://exceljet.net/excel-functions...oduct-function), or you can augment the table that I created for you (see attached).
It's a bit difficult to understand what you are trying to achieve because if you just add up everything then the figure you get is essentially just days that aren't worked. I don't know how useful that is, because obviously a day on maternity leave isn't the same as a day where a person is just late. That beckons the question why would you then need to differentiate between the different types of non-working days.
I fully agree with the others who suggest a database or use of a pivot table, however if you are somewhat new to excel then those options would be goals that you have to work towards.
/Møller