Use an array in the range argument of a countif?

I’m looking for a way to count the number of Permit #s in the lower table—but only once per unique MR #, then put that count in the # of Tickets column in the top table.  The numbers in bold show my desired result, based on the data in the lower table.  I just canʼt pin down a formula to make this work.

To lay out what I’m going for more clearly:

• P-1 has 1 unique MR # associated with it in the lower table.  Therefore, its count in the upper table should = 1 automatically.

• P-2 has 2 unique MR #s associated with it in the lower table.  Therefore, its count in the upper table should = 2 automatically.

• P-3 has 3 unique MR #s associated with it in the lower table.  Therefore, its count in the upper table should = 3 automatically.

• P-4 has 4 unique MR #s associated with it in the lower table.  Therefore, its count in the upper table should = 4 automatically.

Important Notes:

• You canʼt use a dynamic array as the Range argument in a COUNTIF function, else this would already be solved.  (I’ve already tried using various combinations of UNIQUE and COUNTIF, but maybe thereʼs one I’m missing?)

• These are just small pieces of much larger tables in my actual work, and the two columns in the lower table may end up having other columns in between.

• I’ve seen some varying solutions that involve LIST, FILTER, etc., which all rely on index references in the form of {1, 0} etc.  This may be a viable option, but I need it to be bulletproof if the table columns end up getting rearranged.  In other words, I need to be able to reference the range by column name, not by index number.

• VBA and macros are not an option due to company policy.

Thank you for any help you can offer!