Each entry is 64 bytes long; the first 32 are the null-padded name of the place where the special file is mounted; the second 32 are the null-padded name of the special file. The special file has all its directories stripped away; that is, everything through the last `/' is thrown away.
This table is present only so people can look at it. It does not matter to mount if there are duplicated entries nor to umount if a name cannot be found.