If you are the seller you should be fine as the bank works with appraised value. However, the shortfall you are requesting will be higher and there could be tax consequences for that. If you are the buyer, you will not be able to secure a loan for an amount higher than the appraised value so you should have your Realtor prepare an addendum to lower the contract price and you got a better deal. If the appraisal was FHA or VA the seller and their bank will not be able to have it re-appraised for 6 months so that value is locked in for any government backed loan. That should make them receptive to selling it to you at the lower price. Best of luck!
p.s. In our area you don't need an appraisal contingency addendum to protect your rights (although we do use them). If your loan is not approved because the appraisal came in low and you don't have or want to pay cash over appraisal your financing contingency should allow you to terminate as long as the contract specified the loan type and down payment. Again if it's a governmnent (FHA or VA loan) MD has a built in clause that requires appraisal at contract price. *** Always check with an attorney on any contractual issues.