Project GFA excluding underground parking areas?

During the registration process of the project and in the Project Information Form “PI f 2 – Project Summary Details” we were/are asked to indicate the total project gross floor area with an exclusion of all parking areas. This information is automatically linked with the credit form “MR c 1 – Building Reuse – Maintain existing walls, floors and roof”. On the project site the six existing underground levels are located. The existing structure will be reused and the underground parking will be located there. Please advise if we can calculate the total area of the building including the existing parking area using “Special circumstances” path? Thank you in advance!