Each Sunday the app seems to reset my intensity minutes to 0. My VSHR correctly keeps count on Sundays. Both reset to 0 on Mondays as expected.
Also, I've usually met my intensity minutes goal on Saturday, so I was wondering if it was some unclear UI thing where the day after you meet your goal for the week, it displays 0 to indicate 0 remaining minutes needed rather than continuing to increment the intensity minutes gained, but I haven't tested this theory. If I tap the 0 to see the details, it will still show me the intensity minutes earned on each day that week.