The file might be also be being uploaded by other hosts, so you are only supplying part of it. Also the transfer may have been inturupted, which shows as a different message, but think certain interuptions can also show as complete, as quite often the same host will return and upload some more, and if you check you will often find that you can add the percentages of bits of the same file to the same host, and they add up to 100%
I hope this makes sense
