The loan officer is most likely using a credit simulator to estimate the effect of the payment. There is no guarantee that your score will go up 27 points and they should tell you this. The simulators are usually accurate within a margin of error, but there are no guarantees.
You should also note that in most areas, California being one, it's not permitted for you to pay for the Rapid Rescore as a consumer. If you are being charged for this you need to question it.