Extra null sector on DVD
 

I use dd to create two images of a tar file and cdrecord (from cdrtools, not cdrkit) to burn the images. Using several methods to compare checksums, the images themselves appear perfect. After burning, the first image fills the entire 2295104 sectors of 2048 bytes each, and its checksum passes. The second image is 1325791 sectors of 2048 bytes each. After burning, however, and I tried this twice, it gains an extra sector of exactly 2048 bytes of null bits. Comparing only the first 1325791 sectors, the checksum passes. So I'm wondering... why is there an extra 2K?