DSO calculation adjustment in F.30

Hi, All Expert

I have faced a issue that DSO analysis (RFDRRE05) didn't not work as what i want

Detail is like below.

(1) Requirment : I want to exclude the specific GL account 's balance in calculation of DSO' numerator(average AR balance)

(2) Process

    ① SE38 ( Prg: RFDRRSEL, Variant : Copied standard variant)

       - COCD, Open at key date, Dynamic selection (Key point : I have key in 'G/L account' field with specific account what i want to remove )

    ② F.29 - Background batch

    ③ F.30 - DSO calculation result was outcomeded to include a restricted account's balace.

(3) Question : How can I extract the DSO analysis amt to exclude specific account ? or Is this restrict method wrong ?

I am a SAP beginner , so I need a helpful comment of all gurus.

Thanks in advance.