Hi Dr. Guo, 

I found one doubtful point in the slide 8-56 and 8-57 (TORA Detail).  Why does the node A has an offset -2, after B, which has an offset of -2, doing partial reversal to A?  (Shouldn't A's offset become -3?)

Thank you

Because A is sending reflection out. Here the offset value doesn't matter. It can be any value.