Specify a 2- or 3-digit value for EAN prefix

What causes this issue?

You have specified the EAN prefix in an invalid format.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

You must enter 2 or 3 digits for an EAN prefix. This means, for
example, for standard EAN-13s that you must specify the 13th and 12th
or the 13th, 12th, and 11th digits in the EAN. EANs are read from right
to left.
Note
You enter UPC code prefixes with leading zeros.

Error message extract from SAP system. Copyright SAP SE.