I assume that you are entering information concerning income that you received from your pre-tax retirement plan while working as a LEO (not a Roth IRA or Roth 401(k) plan).
It is possible depending on the plan to make post-tax contributions to the plan in addition to the more usual pre-tax contributions.
If you did this, you now have a "basis" (also sometimes called "cost") in the plan.
When you receive distributions from the plan at retirement, then part of the distribution is a return of that "basis" and is not taxable, while the rest of the distribution is taxable.
If you don't recall making any post-tax contributions to your retirement plan, then enter zero or answer no. This will make the entire distribution taxable (as it should in this case). This is also the more common situation for most taxpayers.
