Erase previous codes from 500RGD Receiver

I have a Raynor garage door opener with a 500RGD Receiver on the wall. I've seen posts on here showing how you can program a new remote which I already did and was successful. However, the previous renter never gave back the remotes he had so I am afraid they will come back when I am not home and get into my garage. I would like to know hot to CLEAR all the codes from the receiver so that the previous renter cannot use the remote they kept to open the garage. I cannot find any instruction on how to do this. Any help is appreciated.

I don't believe that you can erase the code on the 500RGD. If you have a 61LM Remote you could try changing the DIP switches in the remote & reprogramming it to the receiver.