your screen grab shows that you are suing the ShipQuantity column and checking for a value of 1:
If the Total Number of Items where 'ShipQuantity' has a value of '1' is '=' a value of '1'
I though you said originally that you had a category column containing the value 'CategoryA'?
This is the column you should be using in your rule:
If the Total Number of items where 'Category' has a value of 'CategoryA' is '=' a value of '1'