i like at the tightest point to have at least 5mm of travel. 10 is fine imo. i like max under 20mm or so
if it's still bothering you, have you tried rotating your chainring (like unbolting it from the arm, then rebolting it one hole over). maybe the arm and the ring are each a little out of round, but they're lined up and working against each other.
i wouldn't worry about it though.