Advanced Settings Changes

Lately, a very high percentage of videos, especially on YouTube are offering 4K videos as the default choice which is basically useless unless you have a 4K monitor. Going into Advanced Settings, I right-click the appropriate box, but rather than allowing me to remove the 4320P to 1280P I only have an option of switching to "Default Values" - see pic below. As I have zero idea what the default values are, I'm not about to make changes that I may not be able to undue. Please advise. Thank you.