I stumbled across this a while ago. It’s a bug in GNU time, values are 4 times too large, as it assumes a size in pages and converts it into kB, even though it is kB already in the first place.
You might wanna check:
http://groups.google.com/group/gnu.utils.help/browse_thread/thread/bb530eb072f86e18/83599c4828de175b
http://forums.whirlpool.net.au/archive/1693957