External no. range -material number both numeric and alphanumeric required

In OMS2, Checked the box(X) , External number assignment without check box.

Number range intervals maintained 00000000000000001 to Z9999999999999999,

Requirement is to go for external number ranges for materials,i was able to create alphanumeric partnumber ,

but when i am creating numeric partnumber (1234) it is throwing me an error.

With this material type, ext. material no. must not contain only numbers

Message no. M3565

Thanks

sweth