Why is there an uncertainly? Yale is very generous in terms of need based aid even for higher income earners.
Is your income in the lower income range? Has anything changed in terms of your financial picture since you sent in your financial aid application forms? Did you get a more generous offer from a peer school?
What reason do you think there is for Yale to give you more need based aid?
How much did they give you? Why do you think this is unreasonable?
https://admissions.yale.edu/financial-aid-prospective-students
Clearly there is something on your financial aid application forms that gave Yale the info they used to compute your family contribution.