Hello, Thank you very much for the response.
I looked at uscis.gov website, M-476 pdf file, however, on page 18, it says 3 years as a Permanent resident.

Does " 2 years and 9 month okay to apply" mean " that I am okay to apply after 33 months but it has to be full 36 months before it's approved" ?
If it can be 33 month before it's approved, is there any document or link talk about this?
I can't find the info regarding this anywhere on uscis.gov website.
By the way, from the uscis doc, looks like I have to add the time that I didn't live in US for the past 2 years after I got my green card.

Thanks a lot