Don’t know if they are talking about some game .ini, but it sounds like it is about SteamVR’s (…presumably still in use…) resolution cap, which defaults to 4096 in the longer of the dimensions of the frame. There is one “steamvr.vrsettings” JSON (…which overrides what is in “default.vrsettings” in the same directory), in the config directory of your Steam installation, and you may have one which overrides that, too, in your user appdata hierarchy.
"steamvr" : {
"maxRecommendedResolution" : 8192
}