My battery levels on P3A were set as-
LOW=30%
CRITICAL 15%
Was flying out of sight and Low battery warning displayed at 32% during RTH
Critical battery kicked in and began auto land at 22% and was a good half mile from Home point.
Fortunately I retrieved it with no damage but why did critical auto land initiate at 22%!!
Battery is new, 20 cycles and good health across cells