You'd need to look at the closing documents from the sale of your house. On those forms, there is a breakdown of the property taxes paid by both buyer and seller for tax year 2017. You'll look for the prorated amount designated to be paid by the seller.
I can't find a prorated amount designated. I only see under Adjustments for Items Unpaid By Seller, County Taxes then the amount, is that what you are talking about?
I'm sorry, but since I can't see your documents, it would be difficult for me to say. Different states have different types of documents and taxes. Maybe you can contact the attorney's office that closed the sale for you for clarification.
The closing documents I've seen typically have a column for Buyer and one for Seller.