Meaning of the first digit : General growing place :
6 : BORDER. Plants with good colouring effects or nice shape, for a open, well drained soil.
Meaning of the second digit: Specific demands :
2 : Plants that are used to complete the border.
Meaning of the third digit : Where to put :
1 : For a warm, sunny place, tolerates occasional dry spells. Note that they do not tolerate very wet conditions in the winter well.