Alternate LT for FA: Change of Transaction creation value in P0025

Hello,

We use an alternate LT for FA. At present, It is settled with: - Post cost from= "AA"

                                                                                        - Transaction code= ''Blank''

Chief account asks for changing Transaction code value by "3" instaed of "Blank", in order to generate depreciation JEs in both AA & alternate LT.

So my question is: If I change it as requested, what are impacts on previous years records and FA process for next periods, years?

See attachment.

Thanks for your help.