There is not a monetary amount that coincides with Box 13 on your W-2. You would only enter something for Box 13 if any of the three boxes for statutory employee, retirement plan, or third-party sick pay have an 'x' or a check mark in the box. These are only used to indicate that the situation exists for that W-2.
So, if your W-2 is blank for box 13, do not check any of the options when you are entering your W-2 in TurboTax.
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