80% Rule

When I'm at home, Mama Lai is a hawk carefully monitoring not only what I consume, but how much I consume.  She has a "ba fen bao" rule (in English it's 80% full).  This is how Mama Lai measures my 80%:

Mama Lai fills my bowl with something healthy, watches me and before I finish she will ask:

 "Are you full?" 

I will shake my head no and as I reach for another helping Mama Lai will take my food away and say:

"Perfect!  That means you're 80% full and it's time to stop eating!"