As I said, I'm pretty sure he's calculating NAV. He doesn't write out the actual calculation there, but he's using some assumptions to get from rent psf to NAV. The actual calculation is relatively simple. Rent psf > rental revenue - operating expenses = NOI / Cap Rate = Real estate value. Then he subtracts the liabilities to get NAV.
I could be wrong, but I'm pretty sure that's what he's doing.