The whole thing is inaccurate.
The hours don't reflect time spent preaching, but actually reflect time spent in preaching mode, which is very different.
If hours represented time spent preaching, the total would be so small that it would be embarassing. Instead they represent the time when you are in preaching mode such as driving, walking between houses, taking a coffee break, chit chatting about vacations, etc etc. I'm pretty sure that out of every hour reported, about 1 minute is actually spent preaching.