-non-zero and not *UNKNOWN*. The I<fraction> argument specifies the
-length of the tick mark as a fraction of the y-axis; the default value
-is 0.1 (10% of the axis). Note that the color specification is not
-optional.
+non-zero and not *UNKNOWN*. The I<fraction> argument specifies the length of
+the tick mark as a fraction of the y-axis; the default value is 0.1 (10% of
+the axis). Note that the color specification is not optional. The TICK marks normaly
+start at the lower edge of the graphing area. If the fraction is negative they start
+at the upper border of the graphing area.