That document is currently editable by anyone so someone could mess up your list (if that is how it works). Maybe you can copy the page and put it into your own google document list. There is a little more to how the page works.
1. The category cell is what adds the item to the weight summary above. Delete the text in the category cell to take the weight out of the weight summary, and vice versa.
2. To add an item, the ounce formula needs to be added to the ounce cell (hopefully you have used excel before to know what I mean). I should have left those ounce formulas in, but don't have time to do that.
3. You can hide or show rows so that your items not taken do not show up in your list.