It's a quick of English (possibly the only language with this feature) where in certain circumstances opposite words can mean the same thing.
The house burnt up, the house burned down.*
I filled in the form, then filled it out again.
(Those are the only two examples I can think of, bit there are probably more.)
*I'm not sure why, but I think "up" goes much better with "burnt", whereas "down" goes with "burned". Do I now come under the "grammar pedant" banner mentioned upthread?
On the dedicated map shelf?
Well go on then, spill the beanz*!
*Heinz, of course