Unless there are sources of income that are reported on your Federal return, but not on your State return, then this entry would not apply and TurboTax would have left it blank. The AL state tax interview in TurboTax will help identify if an entry is needed here.
From 2020 Alabama Form 40 Booklet: If you received income from sources taxable for Federal purposes but exempt for Alabama tax purposes, the source(s) and amount(s) should be entered on line 5 unless they are explained elsewhere on the Alabama return.
EXAMPLE: U.S. Civil Service Retirement is exempt for Alabama purposes and therefore should be shown on line 5.
