Looking at the picture you sent in your last previous post

My example is the result when:
Duplicate Duplicate Reference Row (Left side option) and Discard the Ref Row from Overlay Sheet (Right Side options) are applied.

You see the rose shaded A:2 and A:3 because row 299 of the REF_SHEET matched rows 24 and 25 of the NDS_SHEET. In the normal use case only the first #2669121 is listed.

Other than yours seems to exclude both double Serial Number 10 10 and 9 9, I don't know why your return is only four rows.

Hope this helps. Thank you.