When I run TextDemo, entering either "1,0" or "-1,0", I get (both times):

B-----+-----+
|     |     |
| +---+---+ |
| |   |   | |
| | +-+-+ | |
| | |   | | |
+-+-+   +-+-+
| | |   | | |
| | +-+-+ | |
| |   |   | |
| +---+---+ |
|     |     |
+-----+-----+

So there are duplicate entries accepted? Please clarify the numbering system so I can be absolutely sure I understand it fully and correctly.