It's really nonsensical to state how high the recovery skill is, especially since it is out of the bound of the highest recorded numbers. The king made the Hero wear the slave bracelet because he was the perceived to be the strongest and most valuable person there. If he exposed his abilities and provided results of beyond human healing, surely he will just lead himself to enslavement and become reduced down to a tool. The best solution is to analyze what the range for decent to elite healers and tell people a reasonable number for healing. Though there is one flaw to this, this plan assumes he can control the healing output, if he could only max heal at all times, it is best if he states that his healing is zero so if he want to deny healing service, it can be disguised as inability to heal.