It would be best to enter each fixed asset (computer) as a separate fixed asset, if that data is available, so as to avoid partial disposals however if we use the following model as the current situation.
Note: I am assuming these balances as of your last financial year end’
The fixed asset consists of 3 computers @ 1000 ea - Total 3000 (or if the individual cost is unknown then the fixed assets item’s total purchase cost divided by number of computers)
The accumulated depreciation is 1800 or 600 per computer.
To dispose of one computer you would
a) via Journal Entries Credit the BS Fixed Asset + Item account 1000 and Debit the P&L Fixed Asset Loss on Sale account 1000
b) go to the Fixed Asset tab, click on the Accumulated Depreciation balance for the item and then click “New Depreciation Entry” and enter the date of disposal and an amount of -600 (note the minus sign) and click Create
The result of these two actions would have the P&L showing a nett expense of 400 (1000 - 600).