reg explanation for DAX

Your Calculated column name is - "PoInactive".

PoInactive return value 1 OR -1.

if Count of rows in new_revenuerecognitions which having status " Active" and if count = 0 then return 1 else -1 value.

CALCULATE: Evaluates an expression in a context modified by filters.

COUNTROWS : function counts the number of rows in the specified table, or in a table defined by an expression

FILTER: You can use FILTER to reduce the number of rows in the table that you are working with, and use only specific data in calculations

ALLSELECTED : ALLSELECTED function gets the context that represents all rows and columns in the query, while keeping explicit filters and contexts other than row and column filters. This function can be used to obtain visual totals in queries

PoInactive = 
IF(
   CALCULATE(
     COUNTROWS(new_revenuerecognitions), 
     FILTER(
       ALLSELECTED(new_revenuerecognitions), 
       'new_revenuerecognitions' [PO_Name] in FILTERS(
         'new_revenuerecognitions' [PO_Name]
       ) && 'new_revenuerecognitions' [Status] = "Active"
     )
   )= 0, 
  1, 
  -1
)