Tax Year Prior to 2020: Maryland Estimated tax payment

After completing a married filing jointly 2019 tax return, we received Personal Tax payment vouchers for $293.00 each, once per quarter for an estimated 2020 tax year for the state of Maryland.  We both have jobs in the state and have state  taxes withheld, we also received a refund from both federal and state for 2019.  Can anyone help to as why we are getting these estimated payment vouchers for the following tax year when we got a refund for the previous year?