15? Depends on how many minutes he was studying to get the 1.7gpa. If he was doing 5 then I'd bump it to 15 or so. If he is a complete idiot and pulled a 1.7 while already devoting 15 minutes to studyhall then I'd lower everything to 10 and really crank the studying up.
Btw, low gpa early in a career can cause headaches. Just remember that whatever grades he finishes the year with will kinda sorta establish a new baseline for the next year. Mybe. I think. Well, that's been my experience.