&: Default combination for country & - & to country & already assigned!

What causes this issue?

You have set the flag 'Default combination' for the entry you made for
&V1& from country &V2& - &V3& to country &V4&.
However, the flag 'Default combination' for &V1& from country &V2& -
&V3& to country &V4& is already maintained for another entry.
Since this flag ensures a unique conversion if you have several
entries, it must only be assigned once.

System Response

The system does not allow this entry!

How to fix this error?

Remove the entry for the flag 'Default combination'.

Error message extract from SAP system. Copyright SAP SE.