bsdlabel size mismatch

[Evuraan]

On a FreeBSD 7.2 machine, I've a ~1TB drive as /dev/da0:

da0: 953664MB (1953103872 512 byte sectors: 255H 63S/T 121575C)

the lone slice is of ~19G (per df)  yet bsdlabel shows that it is
spanning the entire drive. also notice how it says unused despite it
really being an ufs FS.

[root at evu ~]# df -h /
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/da0s1a     19G    1.2G     17G     7%    /


[root at evu ~]# bsdlabel /dev/da0s1
# /dev/da0s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a: 1953102296       16    unused        0     0
  c: 1953102312        0    unused        0     0         # "raw"
part, don't edit

needless to say, i cannot edit and add a new partition as "a" seems to
be spanning the entire disk according to bsdlabel at least.

any advise on this would be much appreciated. I am looking to alloc a
16G swap, and add a couple of ufs filesystems to da0.

many thanks in advance.