2 Columns - Want To Count Number of Non Duplicates

It's hard to give you something specific without seeing a sample book, but it sounds like an easy solution might be to use a helper column and COUNTIF. If your first list is in A2:A846 and your second list is in B2:B666, then in C2 try the following:

=IF(COUNTIF($A$2:$A$846, $B2)=0, "Not in A", "In A")

This will return "Not in A" if B2 is not included in the list in A. Fill it down through C666 to get all the non-matches, then use a COUNTIF formula on column C to get your totals. If I have the columns backwards, then just switch the As and Bs in the formula. Hopefully this helps?