I uploaded the wrong file, so you'll need to change the remote type from 15-134 to RCA RCU810. The only 3 digit EFCs will show.

I haven't assigned any buttons at this point and it doesn't matter. We're just interested in the EFCs that you assigned right now.
Regarding removing EFC assignments, that's explained in the 9XX command instructions linked earlier.

According to the Lookup Tool, CBL/SAT 0392 is RCA device 7, and Power is EFC 099. So either the STB also responds to device 15 (at least for power) or the 15-134 is sending two Power IR signals, one for 15 and another for 7. That's why I wanted to know if the STB responded before you set up 0392. You could still check that by assigning CBL to some other setup code temporarily.

If it turns out that the STB does respond to device 15, it may make sense to see if the Combo unit will respond to Power on the VCR or DVD setup codes, assuming that the STB doesn't also respond to those.