condition mean min max ZT0-3 5.5 5.5 5.5 ZT4-7 5.6 5.6 5.6 ZT8-11 8.5 8.5 8.5 ZT12-15 7.05 7.05 7.05 ZT16-19 7.75 7.75 7.75 ZT20-23 6.35 6.35 6.35