Entry with "*" not allowed

What causes this issue?

You want to create a document and have entered the special character
"*" in field <ZH>Document part</>.
This entry is not supported when creating a document.

How to fix this error?

Make a specific entry for the document part.
If you do not make an entry, the system creates document part
<ZH>000</>.
To see which document parts already exist, choose function <ZH>Goto ->
Document parts</>.
In this case, you do enter the special character "*" in the field
<ZH>Document part</>.

Error message extract from SAP system. Copyright SAP SE.