The micro-service is primarily used by the Unified View for the generation of valid reference numbers to the FSA-RN specification and by the Register a Food Business (RaFB) service to generate reference numbers for each registration. The service implementation provides a URL that can be used to request valid numbers to the specification by providing some attributes.
The GitHub page describes the reference documentation and the specification (that is implemented in the micro-service). Standardising Reference Numbers and other identifiers provides one of those enabling components of the broader FSA infrastructure. A reference number needs to be robust. In part this is achieved through the use of check digits that alongside other checks can be used to validate the number. This may be used to help identify number errors that can occur when numbers are exchanged (such as over the phone).