How to differentiate the notation of a compounds charge and an anions oxidations state?
make sure to read up about that topic. The concept of charge and oxidation state are closely related but aren't the same.

Usually oxidation state is written with roman numbers (that's how I learned it) and are not explicitely written like in the example you showed. 

Charges on the other hand are always written (if mentionned) on the upper right side of the anion.

I am far from being an expert, but thinks this might be an answer to your question.