

I asked you which format your music is in and mentioned that it might be relevant. That's a lot, so ask yourself what you have done recently? Have you added a lot more music to your iTunes Library, added a lot more photos to the folder you use for syncing photos (or have you simply specified a different folder, with far more photos in it)? So, all of a sudden you are trying to sync 48GB more to your iPod than you used to do. In fact, since it's not possible to add memory to an iPod, the message is actually misleading.

I'll admit, it's not a particularly "accurate"* message. Therefore, an "additional" 65.7MB is required. The message is explaining to you that you are trying to sync a total of 48.26GB of media to your device, but it only has 47.61GB free.
