Yes it is, I believe SSS for the greens is 70, 71 off the whites. We have blues as well which i think is 73/74
Ladies tees are red and then we have yellow tees as well which match the distance of our smaller course. No idea what the SSS is for these
If the 18-hole SSS for the greens is 70, I find it very, very difficult to believe that a 9-hole SSS is set at 73.
As I said in an earlier post, I would expect the 9-hole SSS to be 1 or 2 strokes less than the 18-hole SSS.
Are your SIs set based on difficulty rather than match play?