How to count the total of locations with the same product as the best seller(TOPN(), COUNT())?

[Anonymous]

I am trying to count the total of locations with the same product as the best seller?

Here is the table, SKU:77Lam05110 is the top sellers for 6 venues. At the bottom of right hand side, I want to get a Sum of the count(6 here).

Below is my code, but it does not work.

Can any one help me, I will really appreciate!

[Anonymous]

This is a bit urgent. I wish I could get help soon.

Thanks!