Multiple countifs ignoring duplicate values in a column

I have seem some example of how to exclude duplicates but I've unfortunately been unable to implement then. I have two tables which I'm using the following countifs statement for:

=COUNTIFS(Table1[FILTERED_RFC_COVERAGE],"*" &Table2[@RFC]& "*",Table1[REL_NUM],[@[RELEASE_VERSION_NUMBER]])

This gives me a result that would be inaccurate because there is a good chance that the total is returning duplicates. A little explanation on the data:

Table1 contains (for simplicity sake) 3 columns; Release Number, Test ID, RFC Number(s). Example:

Release Number  |  Test ID  |  RFC Number

53  |  1  |  1212, 1213

53  |  1  |  1212, 1213

53  |  2  |  1212

53  |  3  |  1213

53  |  4  |  1214, 1215

53  |  4  |  1214, 1215

Table 2 contains single RFC numbers per row

RFC Number

1212  

1213

1214

1215

Because RFC Number is a text field and can contain multiple RFCs, in excel I'm essentially using a like operator to match an RFC number with the RFC numbers column, this is followed by ensuring the uniqueness of release. This currently gives me:

RFC Number  |  Tests

1212  |  3

1213  |  3

1214  |  2

1215  |  2

This is of course wrong, the correct representation would be:

RFC Number  |  Tests

1212  |  2

1213  |  2

1214  |  1

1215  |  1

This no longer double counts the same ID. I believe Frequency or Sum Product could be used but if this can be explained a little that would be great help.

Thank you!