Calories

I'm not into calorie counting that much, I don't log my meals or anything but I noticed one thing that got me curious. According to the app, a leisurely 30 min walk burns almost as many (180) calories as a 30 min HIIT session (220). This seems odd but I don't know anything about how calorie burning works so here I am asking the hive mind if this could possibly be reasonable or if something's off with the app...?