Q: "olcDatabase: {1}mdb" from slapcat: why "{1}"?

I have an amost philosophical question about LDIF and OenLDAP:

Considering dn: olcDatabase={1}mdb,cn=config objectClass: olcDatabaseConfig objectClass: olcMdbConfig olcDatabase: {1}mdb # ...

I wonder why olcDatabase needs the "{1}" when olcDatabase is a single-valued attribute. I understand that "olcDatabase={1}mdb" is needed for ordering the databases within cn=config, But why is the "{1}" repeated for the actual attribute?

When I tried to remove it, I saw that after a slapcat it's there again.

Kind regards, Ulrich