when you try to ask questions in someone else's post on the expert forum, they bump it into the patient to patient forum ( in case you are wondering how your question ended up here ).
if your gf has hsv2 and you don't and you avoid sex
4% is if you don't use any precautions other than just avoiding sex any time she has anything going on genitally. Using a condom would reduce it to about a 3% risk.
4% means, if 100 guys who were hsv2-, had sex over the course of a year with their hsv2+ female partners, 4 of them would contract hsv2 over the course of the year.