The catch in the guarantee to have 100% of need met, is the definition of need. I do urge you to call Yale and ask for a Fin Aid Officer to go over your package in case there has been a mistake. However, often, the way a college defines need does not mesh with the students. If your family owns property or a business, if you have finances unusual here in the US, or a Non Custodial Parent, you can get hit with expectations to tap any of these items when it is not a viable option for your family.
I know families who own farms and properties that have been in the family for generations, and though the land or whatever generates little income, there is an asset value that the schools use. The same if a family lives in a paid for home, and can not afford to pay any mortgage on it. Doesn’t matter. Some schools insist that the value be included in the assets.