Those codes are for your RCA receiver. The RCA receiver does discrete input selection when it sees a specific command for a different RCA device. In those examples, your RCA receiver sees EFC 483 for an RCA SAT or an RCA DVD and does input selection for its SAT or DVD inputs.

"syth" is the name for EFC (advanced) codes on some other models of UEI remotes.

You can temporarily set some device key to be SAT/0392 and test Set 4 8 3, and if it works use the 994 command to key move it to a key in your receiver. Once that key move is done, it doesn't matter that you change the device button that had SAT back to whatever you usually use it for. The key move remains unchanged even when the device key it was based on gets changed.

(Same for DVD 0522).