PA Taxable Compensation is the income subject to Pennsylvania state tax, including wages, salaries, and bonuses. TurboTax asks for this to calculate your state taxes accurately.
You can find your PA Taxable Compensation on your W-2 form:
Box 16: State wages, tips, etc.
If you have many W-2s or moved between states during the year, you'll need to double the earnings for Pennsylvania to make sure they are correct. This step is generally for people who have multiple W-2s or moved between states during the year.