House was represented as 450 square feet more than it actually is.

We are 4 days from closing and the appraisal shows that the house is 1250 square feet instead of 1650. I told our agent that it seemed small but she assured me that if it is in the MLS it could not be a mistake. I really don’t want to just walk away at this point, but I feel that we deserve something for this? Any advice is welcomed as this is our first time buying and do not know how things work?