Copy std wbs issue

Dear Experts,

We are creating the project structure by copying from std wbs.  My coding mask includes alpha and numeric.

My issue is after copying from std wbs system is considering alpha as numeric it is not copying as alpha as I shown in the below example

Std wbs---------------  ABC- 1621-C-D-01

Operative ------------  ABC- 1621-1-1-01

How to resolve this issue.

Thanks

Praveen