The KR10A does the second Light Code. So if the SC1200 is set to House Code C and Light Code 2. The KR10A will do C3.
The SH624 does the Light Code the SC1200 is set to if my memory is correct.
You can test this by temporarily setting the SC1200 to Light Code 1 and see if the KR10A then controlls the Socket Rocket on C2. Then the SH624 Security Light buttons may not control it. Though the 1-4 unit code buttons on it should still access the Socket Rocket with its #2 button set.