A bunch is not a standard measure, so the size will vary. In general, they are about a pound or slightly less for a medium-large bunch. They usually have 5 to 7 stems, and once cut, will yield about 5 to 6 cups of loosely packed chopped leaves plus a cup or more of chopped stems per bunch. While this may not be reassuring if you are bringing in chard from your garden, the good news is that this recipe is incredibly forgiving so no matter how big or small your chard bunch is, it should work fine as written. Or simply adjust the seasonings to your taste preference.