For state taxes, your double-taxed income is income that is taxed in both the state you work in and the state you live in. This is common when you live and work near state borders and, in some cases, when you work remotely for an employer based in a different state.
When preparing your tax return, it's usually best to prepare the return for your nonresident state (the state you work in) before preparing the return for your resident state (the state you live in). That way, TurboTax will automatically calculate any tax credit you may qualify for due to paying tax on the same income twice.