Iphone Audio space usage doesn't match music?

i don't think i've ever seen this before on my prior ipods, but maybe i'm missed it, but...

i am finding the "storage space" used by audio/music in my iphone listed in the general tab does not match the actual music on the device.

eg, for 126mb of music (one album), it shows 961mb used; if i add a few more albums worth 268mb, the total space used goes up to 1.08gb

in other words, there is a phantom 800+ mb unaccounted for. anyone else seen this?

moreover, with 16gb of music on it, it suggests the audio usage is over 19gb...

i just checked my ipod touch which has 50.2gb of music on it, the "capacity meter" reports 50.9gb of usage...closer but sort of similar? does the iphone 4 have a different file system?