How high is the box? (I want to compare it to what I work out with)
An above post already said what I would recommend, don't go that low (some would recommend it though) and make sure to drop quickly to generate power like a spring.
I want to add one thing though, ok two.
1. It's hard to tell because of the pics and I'm sure you not only know this but are doing it: explode up with your arms very very fast to help generate power, it will prepell you up higher.
- As a box jumper myself, you should be landing in or near the middle of the box, or mats or whatever you have. Not only for safety, but when you are landing in the middle consistantly, you step it up an inch or two etc, etc. Then you work at landing in the new height in the middle consistantly and step up the height. That way you won't plateau as quickly and you can adapt better. I'm just ranting but I'm sure you know all this. But then again everyone's techniques are different and who's to say mine is better.