SCO osr5's logical volume starting

Hi
My query is regarding the logical volume start. I am using sco open server 5.0.7. I create 3 volumes

  1. / 5000 Mb
  2. /home -2000Mb
  3. /sundeep -500MB

The document of SCO says that the logcal drive start from the 1st block of fs. From the disk label when i jump to the start of the partitions .I found the superblock about 273106 sectors(133mb) away the stating location og partition. The same thing happens in all the partitions.
Why this happens. I tried several times and make different size of partitions.Even i make 100mb partitions but the locations of superblock structure found after the 273106 sectors.(very amazing)

Again i tried on different system with different Hard disk(SCSI) but next time i found the super block position after the 16065 sectors from the starting of partion.

How i found this value and in which structure this value is defined.

Plesae guide me

Sundeep saini