Calorie counting with workouts.

I'm trying to find out just how accurate the calorie counting is while doing a workout vs. normal day wearing. I forgot to press stop after a gym workout and my workout timer went for 45 minutes passed the time I stopped my actually "working out". Now obviously I know my calories burned during that specific workout were higher, but my daily total was over 150 calories more than the day before, in which I did the same workout without the extra time. I tested it the next 2 days by trying to do the same thing all day, except I let my workout one day go 1 hour over. Day 1 I did a 30 min jog and the next day a 30 minute job but let my timer go to 90 minutes. Even though I wasn't jogging, my daily calorie total was over 250 calories more on the day I let my workout timer go for an hour longer. Can anyone shed light on whether or not the calorie counting is better/more accurate during a workout.

Thank you