LDAP ownCloudQuota attribute not working or able to be applied : need more documentation

We have a working LDAP server (openldap). We have an OwnCloud server working with that LDAP server for authentication.

When I added the LDIF for the OwnCloud schema, it was added correctly and shows up.

ldapsearch -H ldapi:// -Y EXTERNAL -LLL -b cn=config "(cn={*}owncloud)"
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
dn: cn={14}owncloud,cn=schema,cn=config
objectClass: olcSchemaConfig
cn: {14}owncloud
olcAttributeTypes: {0}( 1.3.6.1.4.1.39430.1.1.1 NAME 'ownCloudQuota' DESC 'Use
r Quota (e.g. 2 GB)' EQUALITY caseExactMatch SUBSTR caseIgnoreSubstringsMatch
SYNTAX 1.3.6.1.4.1.1466.115.121.1.15 SINGLE-VALUE )
olcObjectClasses: {0}( 1.3.6.1.4.1.39430.1.2.1 NAME 'ownCloud' DESC 'ownCloud
LDAP Schema' AUXILIARY MAY ( ownCloudQuota ) )

However, in my LDAP management tool, if I try to add an attribute of ownCloudQuota to one of the users, it tells me that "according to the schema attribute ownCloudQuota is not allowed."

What are the requirements for the owncloud schema and its attributes to work and play ball nicely with other LDAP schemas?

My users in this LDAP database have inetOrgPerson as the structural ObjectClass.