Formula to consider first value of multiple same values

Hello formula experts
I am facing an issue with the formulas in columns L and O. When the amounts are same under one GSTIN number, the formula is selecting all the amounts and displaying matched. I need your expertise to edit the formula in such a way that it will select only one row (first row) to match and the remaining ones as blank. The code needed to be edited are columns L and O only as they do not take the Invoice number and Date into consideration. Please help me to solve this issue.
Thank you in advance