COUNTX Counts the number of rows that contain a non-blank value or an expression that evaluates to a non-blank value, when evaluating an expression over a table.
Syntax
COUNTX(table,expression)
Parameters
table – The table containing the rows to be counted.
Expression – An expression that returns the set of values that contains the values you want to count.
Return Value
An integer.
Reference Data
https://docs.microsoft.com/en-us/dax/dax-function-reference