I have never really followed the feeding chart but then again I have been keeping snakes on and off for 30+ years and eventually you can just look at the rat and determine if it is an appropriate size. I feed mine FT Rat pups until they are around 100 grams, then move to FT weaned rats until 350 to 400 grams, then move to FT small rats until they are 1000 grams. At around 1500 grams I alternate with a FT small one week then a FT medium the next week until 2000+ then it is always a FT medium.