This isn't exactly true. Yes you burn about 400 calories during the exercise but you also speed up your metabolism for days so its gonna be considerable more.
I think the main thing if you wanna see weight loss is cutting out as many carbs as you can. So no drinks with sugar, starches, potatoes bread etc. and only exercise a few times a week but make it count as in minimum 15 minutes of cardio that leaves you sweaty and out of breath. This is enough to keep your metabolism high even when sitting on a couch and watching movies all day. Also no matter what you do, you're right. Fat has a lot of calories in it and is slow to burn so patience is the key. It's unlikely you burn more than a few pounds per week no matter what you do.