8 Y Axis
From TrueERP wiki
Can you change the Y Axis?
The first Attribute entered for a product will be the Y Axis or Vertical Axis by default. This can be changed later by selecting another attribute from the drop down list.
The X & Y Axis are important because they will define how the product attributes are displayed in a grid. These should be the two attributes most often selected in an order. Ideally the attribute with the least number of values should be the Y Axis as a horizontal table is easier to read than a vertical one, unless there are so many values that they won't fit on screen.
