I tried reading carefully for a long time earlier. I could't see why the exact same data for the exact same penetration, .00 to 4.50, gets a different column 7 in 6.17A than the same data gets in 6.21 and 6.21A. I guess reading comprehension is a weakness with me. Is column 7 something different in 6.17A than in 6.21 and 6.21A? I saw no explanation of a difference that would explain the same data getting a different answer in table 6.17A column 7 than in 6.21 and 6.21A columns 7.