They're likely referring to the fact that x86-64 only uses 48 bit addresses (they're sign extended to fit in a 64 bit register/memory block). As to why they cho

They're likely referring to the fact that x86-64 only uses 48 bit addresses (they're sign extended to fit in a 64 bit register/memory block). As to why they chose to use this in marketing instead of 64 bit, that is a mystery.