Employee
Month & Pay
From the employee's record — to change it, edit their entry on the Employees page. Unplanned/Unpaid Leave (below) is deducted automatically on top of this.
Extra Earnings (added on top of net pay this month)
Giving an advance this month? Enter it here — recover it via "Advance" under Deductions on whichever future month's slip you repay it.
Deductions (every month)
Other Deductions (occasional, only when applicable)
Leave

Unplanned/Unpaid Leave is independent of Last Working Day above — leaving the company isn't "leave".