Thanks for the suggestion but it looks like the suggested fields can't be used to add up total stopped time in a report.
i.e. the_Running fields seems to just indicate real time if the clock is running right now or not.
Had a look in the data dictionary before also and didn't see any fields track total time SLA clock running or stopped.
Theoretically a call can have the clock stopped more than once also. So if there is no counter in the call logging table I think I am forced to look in the problem history activities to figure out when times stopped/started and calculate the durations.
Thanks anyway mate