HD channel comes from both 99 and 103 sats. the "S" satellites are spot beams. dont worry about them.
you can find the satellite map here
To expand just a bit on peds48 comment - both 99s and 103s are spot beams for local channels. That means that you should have one or more transponders on those specific satellites with a high reading, but you don't need to worry about all the transponders with low or zero readings as long as you are receiving your local channels properly.
The other HD feeds on 99c and 103ca/cb should have high readings on all active transponders (high 80's or 90's), as well as 101 (for SD channels).