How to Countif filtered data

Hi

This will count 4

Formula:

=SUM(IF(FREQUENCY(IF(B6:B45<>"",MATCH($B$6:$B$45,$B$6:$B$45,0)),ROW($B$6:$B$45)-ROW($B$6)+1),1))

This is array formula. Press same time (Ctrl+Shift+Enter) till you see both end{}. DO NOT PRESS ENTER ON IT OWN? Otherwise it won't work