Thinking about this a little more, I presume the "empty" cells must actually have a text value in them otherwise SUBTOTAL wouldn't count them, you can probably get the right result without the extra condition, just by changing the 3 to a 2 in the SUBTOTAL function, that will then only include cells with a numeric value, i.e.
=SUMPRODUCT(SUBTOTAL(2,OFFSET('Y4 R'!$AT$16,ROW('Y4 R'!$AT$16:$AT$120)-ROW('Y4 R'!$AT$16),0)),('Y4 R'!$AT$16:$AT$120>=5)+0)/'Y4 R'!L10
Bookmarks