Total income means everything you receive from all taxable sources. That means you need to include things like pensions and interest on your savings in a building society before the tax has been taken off.
Don't forget if you are married/in a civil partnership, a basic rate taxpayer and your partner does not earn enough to pay tax or earn at all, they can transfer 10% of their personal allwances to save you a further £250 in tax
There are three levels of Personal Allowance
Personal Allowance 2020-21 tax year
Income limit Basic £12500 Basic rate £12501 to £50000 20% Higher rate £50001 to £150000 40% Additional rate over £150000 45%