The rtp_timeout options were the options that the author of the other post wanted to set; they are not the ones you want to set.
type=aor, as I said, is something that should go after the “+”, not in the body of the settings. Basically the [302] selects the section, the “+” means you are appending to section, and the type would indicate that you were appending to the one of that name that already contained that type setting.
As I said, I suspect that is the wrong file for an aor. If I understand the naming conventions, used by FreePBX, I would expect the file to be called pjsip_aor_custom_post.conf, but I’m really an Asterisk person, not a FreePBX one.
As it says in a more general answer to the question of dealing with options missing from the GUI (Change PJSIP settings - #4 by lgaetz), you need to change the appropriate file. I didn’t use that example because the example I used was more concrete, but it still has to be treated as an example of general principles, not something to be copied blindly. The other option listed there has already been used, as there is an issue requesting the addition of the option.