To DELETE any transaction lines/products etc:
Highlight the transaction lines to delete by pressing each record box usually to the far left of the transaction line and press the DELETE key, please note this is NOT the backspace key. Or you can go to the Edit menu above and find Delete Record option (transaction lines must be highlighted first). Pressing/selecting either of these will bring up a message asking if you want to confirm deleting, say yes to confirm!
The DELETE or DEL key is usually located in the upper right hand side of the keyboard!