I have no idea where you heard the 12% number, but that's not how the process works. At the time of certification of an application (under the ordinance currently in effect), the owners of 51% or more of the properties in the affected area, owning in aggregate 51% or more of the area of the properties in the affected area, must have signed the petition. Up until the public hearing for the HAHC meeting at which the application was certified, signers could be removed or added. (Both happened.) Similarly, the edge boundaries could be adjusted up until the HAHC voted to certify the application. (This also happened.) At the time of the vote, the HAHC certified that >51% of the ownership (in both senses) of the proposed historic district had signed to approve the application (and not rescinded their approval), as required by ordinance.. The remaining <49% or so may have declined to sign the application, eluded contact, signed and retracted, wanted to sign but never got around to it, hated the idea, or just not cared; we don't know how many fall into which category.