@Kaleigh Griffiths Access to the garage and "parking rights" or permission to park on a driveway or in front of the garage are unfortunately not the same thing. In San Francisco, a "traditional" suburban driveways are rare and are often times confused with the sidewalk portion in front of the building. It sounds like the top tenant might be trying to use the street space in front of the garage door as an opportunity to park in a city where street parking is scarce.
Because the "driveway" is technically the sidewalk in many parts of San Francisco, it is not permissible per the SFMTA for a car to be parked on it at anytime. It is therefore possible for anyone including a pedestrian, neighbor or in this case the top tenant to call DPT and have the car cited for blocking the sidewalk.
If however, your lower level tenants are parking along the street in front of the garage, it should not be possible for the top tenant to call DPT for a complaint. The only citation that could be issued would be for a blocked driveway, but DPT does requires the individual reporting the blocked driveway to show proof of access to the building garage which is usually evidenced by opening the garage door.
Two parting thoughts for you. First, assuming the driveway is indeed the sidewalk, as I suggested above, it is not covered by your lease agreement and the top tenant nor the lower tenants have any usage rights. Second, contrary to suggestions above to clarify or modify the lease, in SF it is against the local San Francisco Rental Ordinance to unilaterally make changes to an existing lease agreement.