COUNTX is an iterator function that counts non-blank results of an expression evaluated row by row over a table.
Count Reviews >= 5 = COUNTX('Table', IF('Table'[Review Points] >= 5, 1, BLANK()))
When you need to count based on an expression that is evaluated for each row in a table.
Go to report view
Insert a card
drag the newly created measure "CountX" from the date pane into card
You will get the CountX displayed in the card