In my game table we have a simple question since we are not english native-speakers. Does the wording of the Extended Action say you can add a degree of success to one successfull Ballistic Skill Test or to all successfull Ballistic Skill Tests during that turn?

Wording is a little bit unclear for non-native english speakers, I agree.

It allows you to add one extra degree of succes to ONE succesfull balistic test made with ship weapons during that turn.

Thank you very much! =)

We were doing it wrong, then.