MySQL compute percent change
SELECT `Column`,
       Amount,
       COALESCE(LAG(Amount) OVER (ORDER BY `Column` ASC), 0) `Previous Amount`,
       COALESCE(100*(Amount -
                 LAG(Amount) OVER (ORDER BY `Column` ASC)) /
                 LAG(Amount) OVER (ORDER BY `Column` ASC), 0) `Percent Change`
FROM MyTable ;


fiddle

PS. It's extremely bad practice to store number data in VARCHAR field.

PPS. While using any ticks always look for a proper tick type.