The original formula looks like this:
<code>
=SUM(COUNTIFS(Details!$BA:$BA,"A",Details!$AZ:$AZ,">"&"2018-12-31",Details!$AZ:$AZ,"<"&"2019-4-1")+(COUNTIFS(Details!$BA:$BA,"N",Details!$AZ:$AZ,">"&"2018-12-31",Details!$AZ:$AZ,"<"&"2019-4-1")))
</code>
The purpose of this is to feed into charts...