Time Defending vs Time Defended

I have a Vape thats been defending a gym for 1 day 22 hours and 6 minutes, but under time defended in Total Gym Activity, its listed as 0 days 0 hours. For a different gym, I had a eggy in there for 1 day 10 hours. It got kicked and I now have a Snorlax in there. The snorlax has been there for 21 hours but the Time Defended hasnt changed at all since my eggy was returned to me. What leads to these discrepancies?