@Johnny ***********
you did not get a 30 day extension on a 90 day Non-Immigrant visa entry of ANY kind :/ They don't exist
AND just so you're clear, Amnesty last year started on March 26th and ran until Oct 31st SO if it was in May 2020, you either were on amnesty (which means you didn't NEED a stamp OR you got a 30 day "embassy request" extension with a letter form your embassy.
One last time there is no 30 day extension available to people on non-immigrant type visas