SQL for candidate step and status

Hello,

I am using the following formula in a report to capture the average number of days from the 3rd interviewed date to the offered date. We are using the 3rd Interview Reference Model twice in 1 CSW, so how do I specify which 3rd Interview date I want the formula to use?

AVG(TIMESTAMPDIFF(SQL_TSI_DAY,"Submission Dates"."3rd Interviewed Date","Submission Dates"."Offered Date"))

Thank you!