How does the Personal Tip get computed if I have a personal charge and a tip?

I have a total charge for dinner for $46.96 and $9.39 Tip and Personal $0.61


Total Charges not including Tip +	$46.96
Personal +	$0.61
Tip	$9.39
Total	$59.96
Personal -	$0.61
Personal Tip -	$.12
Net Total	$56.23
Due Employee to Company	-$.73

How the system compute Personal Tip

Personal ratio = Personal Amount /Total with no tip= $0.61/ $46.96 = 0.012989

Personal Tip = Personal ratio * Tip Amount = 0.012989 * $9.39 = $0.12