2.1.1583 Part 1 Section 21.2.3.8, ST_Crosses (Crosses)

a.   The standard states that the autoZero value specifies that the category axis crosses at the zero point of the value axis (if possible), or the minimum value (if the minimum is greater than zero) or the maximum (if the maximum is less than zero).

Office uses this value to specify that one axis crosses the other at the zero point, if a zero point exists; at the minimum value, if the minimum is greater than 0 or the axis is not numerical; or at the maximum value, if the maximum is less than 0.