In the fixed asset retirement window, if you enter proceeds w/ 100% of asset on the first line and then tab-through to the second line, there is a prompt that denotes you cannot create a second line when there is no % and/or qty associated w/ that line.

If you BYPASS the warning to the user and manually click in the 'Expenses of Sale' field on the 2nd line, you won't receive the error message, you'll receive the 'Return Code 17' error message after clicking 'Retire', AND you'll receive a G/L batch that does NOT balance.