A comparator placed to measure a brewing stand uses the wrong formula to calculate its power output level. This causes its output to be one level too low most of the time. It is only correct when it is completely full or when it contains no water bottles and less than 19 items of an ingredient that stacks to 64. It never outputs level 14 at all; with 3 water bottles and 63 nether wart it outputs level 13. If you then add 1 more nether wart it jumps to 15.