I see now what's happening, and I have you to thank. The IRS is splitting the difference. 70,150 is 7,954. 70,200 is 7,960. 6 dollar spread. To simplify things, the IRS splits the difference. Thus, at 70,175, the middle of the range, it's 7,957--right in the middle of the difference. So, they are not strictly following the math. But, the math makes sense now.
