To increase income without affecting banking, create a general journal entry (My Company . Make Journal Entry)
Enter date
Choose an income account and enterv27 in the Credit column. Tab to next line. Enter Owner Draw, your equity account used to track what you remove from business and the 27 should already appear in the Debit column.
Click Save
This essentially says you personally pocketed the previously unaccounted for $27.
If you instead must reduce income, post income as debit and equity as credit. This would represent that you added the missing money from your personal funds.