What's the difference between running and total times when doing process ana

I ran a side by side comparison of the two out of curiosity. I got the same number in each column for any given process.
However I did notice that the function definition in Designer for Running Completion Time says:
"The same as Total Completion Time but if a task is not yet accepted it calculates completion time using current time".

That's what the documentation says. What does it mean exactly?

I believe all it means is that if there is an active task in a process, Running Completion Time is the difference between now and the time the task was assigned.

Total Completion time: it may take time for which the task is paused.
And total running time may not.