How long should a thesis proposal(/lit review) be?

Hi all!

I've been watching YouTube videos and reading articles about writing my thesis proposal and some say the whole thing should be 2-3 pages, some say 5-8. My thesis advisor said the lit review alone is typically like 6-20 pages. I just wanted to know what's normal because I can't find anything comparable to that online but also, this is my advisor, so whatever I do should match their standards, right? Any advice welcome.