It says I have a tax overpayment, and asks if I want to apply it to my 2017 return. Does this mean I owe money?

[ThomasM]

No, you don't owe money.  What it's telling you is that you have a refund (overpayment) and you can choose to take it now or you can elect to carry it forward to your 2017 tax return (instead of taking it now).

Unless you're self-employed and customarily make estimated tax payments -- or you're worried about owing money in 2017 (maybe you plan to sell property or you anticipate a spike in income) -- then there's really no reason to carry it forward.  It's just something the IRS allows you to do if you want to.