Agreed. List the property as it is currently identified on City/Public records. If something's amiss, and the City record does not match the physical layout of the property, state something to that affect in the disclosure line of your MLS or attach an addendum to minimize any potential misrepresentations or legal ramifications. CYA - all the way!!! Good Luck!
Same as the other post, can you clarify? Don't lower the unit count to two from three, especially if you have a third unit. Below grade or not, if the building is a three flat on city records, keep it that way.