just a snapshot from synopsys wesite:
Each column specifies the value of the switching activity from a specific source:
From Activity File : The switching activity value is from a SAIF or VCD file.
From SSA : The switching activity value set by using the set_switching_activity
command.
From SCA : The switching activity set by using the set_case_analysis command.
From clock : The switching activity set by using the create_clock command.
For rest its straignt forwarded...
that switching activity which is not propagated, which are not default, those whaich are not implied on nets, those which are not annotated and rest is total.