All thresholds in Subsections a and b, above, shall be interpreted to apply cumulatively over time on the lot as it existed, beginning as of the effective date of this section. If or when any one of the thresholds is reached, this section shall apply to any and all development in excess of that threshold. Where an application proposes a mixed use, the thresholds in Subsection b, for non-residential development, shall apply to the whole of the project, while that in Subsection a shall apply to the residential component.