Quick Exploding animation

I’ve made an animation that explodes a box and reveals text that’s inside it.

However, I can’t make it explode from the left->right. For some reason it starts from the right hand side of the cube.

I’ve tried to google it but cant find it. Also tried to check the settings but cant find it.

Some help would be awesome!

EDIT 1:

Hi. 30Mb max limit on that page.
So i uploaded the blend file here
https://forumfiles.com/j942T5Hdoe/killlah_wood_blend