The additional tax is "surtax".
https://www.canada.ca/en/revenue-agency/services/forms-publications/payroll/t4032-payroll-deductions-tables/t4032on-jan/t4032on-january-general-information.html
Surtax
For 2022, the Ontario's surtax is:
where the basic provincial tax payable is less than or equal to $4,991, the surtax is $0
where the basic provincial tax payable is greater than $4,991 and less than or equal to $6,387, the surtax is 20% of the basic provincial tax payable over $4,991
where the basic provincial tax payable is greater than $6,387, the surtax is 20% of the basic provincial tax payable over $4,991, plus 36% of the basic provincial tax payable over $6,387