If you wish to count the same or duplicate values in a column only once in Excel or the count of occurances of duplicate values, read this article.

Learn how to combine Microsoft Excel’s ROW() and ROUNDUP() functions to create a flexible serial function that returns groups of consecutive values.

If you need to average a list of values in Microsoft Excel that contain duplicates without including the duplicates, don't fret over a complex expression when you can easily remove those duplicates.