The image you have provided references a tube, therefore I would guess that they are referring to the axial and hoop direction only because the structure they are testing is a cylindrical shape. If you were to split the cylinder and roll it out into a rectangle you will see that this is the same as defining cartesian properties. You can define the axial direction as Z, the Hoop direction as Y, then use a cylindrical coordinate system to define the element orientation. X would be the radial direction, which is not in the information you have provided, but you may be able to estimate or source elsewhere.