Seems like you need to add one more field to the Job table: Referral ID.
Then you can set up this relationship:
Referrals::ReferralID = Jobs::ReferralID
Referrals::ReferralID would be defined as an auto-entered serial number and Jobs::ReferralID would be defined as a number field.
Is that the relationship you have set up here? If so, please describe the design of your layout where you appear to be getting duplicate records.