Look at the amount on the voucher, Form 1040-V. Is it the same amount as shown on the Form 1040-X Line 20?
I do not think a voucher is used for a tax payment on a 2019 federal amended return. You would write a check for the amount owed and mail it with the amended return.
See the Form 1040-X Instructions (2019) for paying by check on page 16 - https://www.irs.gov/pub/irs-prior/i1040x--2019.pdf#page16
You can also pay the taxes owed on the IRS payment website using Direct Pay - https://www.irs.gov/payments
The address for where to mail your Form 1040-X with a payment when living in Indiana is:
Department of the Treasury
Internal Revenue Service
Kansas City, MO 64999-0052
Go to this IRS website for where to mail a form with or without a payment by state - https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
