» Counting number of unique entries in a specified range.

Solution:

By using SUMPRODUCT along with COUNT to count only the number
of unique entries in a specified range.
The range can be all in one column or row, or may span multiple (adjoining) columns/rows.
The formula would be written as: =SUMPRODUCT((1/COUNTIF(A1:C5,A1:C5&"")))
where A1:C5 is replaced with the range you want to apply the count to.
Screenshot // Counting number of unique entries in a specified range.