Within the online references feature there is a field for the applicant to nominate the Qualification of the referee. This is a drop-down field that will display the custom qualifications you have set within your masters.
To create or edit your qualifications in your setting please visit: Masters > Referee Qualification
To add a new Qualification select the 'Add new Referee Qualification' option.
To edit a previously entered qualification select the edit pencil
On the selection of the pencil it will expand the settings to allow you to update the field.