Different dump files for the same discs?

[Grayvas]

Last week (Wednesday) I provided two dump files to the email (svq@makemkv.com) for two separate blue ray discs containing the Fate Stay/Night 20th Anniversary Concert. However when I tried opening the discs today, I got two new dump files with a different name and file size. I am wondering what caused this. I assumed that I would need to sent these dump files to svq@makemkv.com as well, so I did.