Because you have "share Incomplete files" in the LW configuration enabled.
If you have a fast internet connection, it will help to speed up the download of that file, since other users will be finished uploading the file faster and hence there will be more hosts free from which you can upload.
If you have a slow (i.e. 56K modem) connection, you might want to disable it.
Go LW>Tools>Options>Share and untick the function mentioned above.
