A "bowlful" refers to the amount of something that can fit into a bowl. It specifies the quantity or measurement of an item that can fill a bowl. Full definition
I use to snack on these in the afternoon before heading into a night of serving at the restaurant, or curl up on the couch with a small bowlful for a movie night with Scott. (faring-well.com)
Now she will have a big bowlful of beans for breakfast. (nourishingmeals.com)