When you first get your tamagotchi you have to feed it 4 meals and 4 snacks before you do any thing. Next if it is too big then you have to play games and get money or to just get you tamagotchi in shape. If you have it over weight the numbers for it's weight then the numbers would be 30 or below. Thats how you know your Tamagothi is in shape. 
So have fun with your tamagothi and keep it non harmed and helthy. 
So have fun with your tamagothi and keep it non harmed and helthy. 
