Nicu mom question

I posted a couple days ago asking nicu moms when they had there baby and how long they were there well today I went to the nicu as I do to visit my baby that I had at 34 weeks 6 days, he weighed 5 pounds 12 oz. Well nothing was medically wrong with him he just had a hard time taking bottle feeds and well yesterday he started taking bottles showing all the signs he’s ready we’ll the nurse said he’s taking 76% of the bottles and needs 80% to go home, the doctor came in today and I asked how long he has left as a guess and he said less then a week, does anyone have experience with this? Or anything I have no clue what the 80% rule is? Could anyone tell me? I asked her but she didn’t really give a clear explanation. Also to add he’s gaining weight as he should