RAM SS Noncomposite Floor System

Hello,

I am having trouble finding guidance on the inputs for Deck/Slab Property Information>Noncomposite  Floor System in the modeler.

I am using a 1.5" deep PLB Verco Roof deck. Under Diaphragm, would the effective thickness be the thickness of the gauge metal (20 GA), the overall thickness of the metal deck (1.5") or somewhere in between??

Thank you!!