wrong sector count in dumpfs -m newfs -s arg

Here it is

/dev/twed0s1f is 199 636 542 1K blocks in size

osiris#dumpfs -m /dev/twed0s1f
# newfs command for /dev/twed0s1f (/dev/twed0s1f)
newfs -O 2 -U -a 8 -b 16384 -d 16384 -e 2048 -f 2048 -g 16384 -h 64 -m 8 -o time -s 103062480 /dev/twed0s1f

osiris# geom disk list
Geom name: twed0
Providers:
1. Name: twed0
   Mediasize: 240066101248 (224G)
   Sectorsize: 512
   Mode: r5w5e6
   fwsectors: 63
   fwheads: 255

As you see the sector size is 512.

newfs from dumpfs -s arg says this fs
is 103062480 sectors long

512*103062480= 52 767 989 760 bytes 
or
51 531 240 in 1K blocks

And i thought it should be exactly he size of the filesystem.

Any idea what's up with this?

--
Artem