Hello!
If I understand the question right, you have the interactive data class (SAP) with 30% guarantee in addition to the 2 other classes viz. IP LAN-to-LAN (40% guarantee) and IP ACCESS (remaining). If this is the case, then whenever the SAP traffic is bursting above 30%, it will use the bandwidth available in any of the other classes. if the other classes are completely using the entire bandwidth, then the SAP traffic will be limited to 30% and rest will be tail-dropped in the queue.
So when there is free bandwidth available in any of the classes it can be used by any class that requires it. There is no tracking of "from which class" the bandwidth is used. Imagine like the free bandwidth from all the classes is present as a lot and it is used by classes that need it.
Regards,
Niranjan