Box borders don't line up?

[TrultToast]

Thank you very much Mike and Mark!
When I tried Mikes suggestion. It sadly did nothing, but when I did what mark suggested and put Mikes code in my additional.css file under the class "#info", it did work.

Thank you both very much again!

edit:
Just out of curiosity, is there a reason why I need to keep adding this to some of my boxes? Like what did I do wrong to make 100% not work correctly without adding "width: calc(100% + 2px) !important;"??