Why is there a discrepancy in disk usage reported by df and du?

This page gives some insight on why they have different values, however it seems to suggest that your du size should be the smaller of the two.

df uses total allocated blocks, while du only looks at files themselves, excluding metadata such as inodes, which still require blocks on the disk. Additionally, if a file is deleted while an application has it opened, du will report it as free space but df does not until the application exits.

When du is larger than df, the usual reason is "sparse blocks": if a program doesn't actually write to a disk block but instead seeks past it, it gets a zero pointer in the inode's block allocation map and no actual disk space is reserved for it. If you later write to it, an actual disk block will be allocated and the map will be changed to point to the new block.