The deleteLine() function runs on the line where the cursor is placed. When the trigger fires, the cursor will be on the last line of your and trigger. If you know where the other line is relative to that, you can move the cursor using the moveCursor() function, and then call deleteLine() to delete the line you moved the cursor to.
In this case, assuming your trigger fires on the line with all the numbers, you could do this:
moveCursor(0,getLineNumber()-2)
deleteLine()
That would just get rid of the top line. I haven't personally played around with deleting multiple lines at a time, but you may just be able to call deleteLine() a few more times to cut them all out. A little experimentation should sort that out fairly quickly, I would think.