The file header record expresses the number of cases in the system file as an int32 (see File Header Record). This record allows the number of cases in the system file to be expressed as a 64-bit number.
int32 rec_type; int32 subtype; int32 size; int32 count; int64 unknown; int64 ncases64;
int32 rec_type;Record type. Always set to 7.
int32 subtype;Record subtype. Always set to 16.
int32 size;Size of each element. Always set to 8.
int32 count;Number of pieces of data in the data part. Alway set to 2.
int64 unknown;Meaning unknown. Always set to 1.
int64 ncases64;Number of cases in the file as a 64-bit integer. Presumably this
could be -1 to indicate that the number of cases is unknown, for the
same reason as ncases in the file header record, but this has
not been observed in the wild.