They ought to call them 4 ups.
Edit: on second thoughts I think i see the point. x-up suggests adding a fixed increment x times, in this case the increment is the size of the original. So a 1 up would be twice the original size and a 2 up would be 3 times etc. Am I right?
I labour the point because I, like a lot of people it seems, always assumed 3 ups were 3 times the size.