Twice as big horizontally and twice as big vertically. Make an 6000x4500 empty image in image editor and see, how many child posts you can paste in it.
But then again Tewi's hair isn't normally that long.
Nor are her boobs that big. Could be an "age progression" thing. Could also be an error. Or, maybe, just another rabbit. There are several in the Bamboo Forest, maybe one is just that stacked.