Ya sorry, a bit of an exaggeration there. I was recalling the size of the hard disks that some folks routinely kept around just for storing crypto blockchains. That said, the actual numbers are already out of the rang for storage on the vast majority of commercially available mobile devices which basically relegates cryptos to enthusiasts. If we could fit a year worth of transactions in to on the order of 10 gigs, or at least provide a constant size estimate per unit time as a function of the number of transactions then we might be able to get adoption.
Well a full node doesn't need to keep the full block chain around, just the UTXO set. But you're not going to be able to handle the bandwidth of a full block chain on a mobile device anyway (~1TB/mo).
The number you describe is a constant "change in size." What I describe is a constant maximum worst case "size." Yours would be velocity, mine would be position, function, derivative, etc.