Why is my pension deduction amount not 2000.00 when I have t4a income, it is only using 1019.00

If your Eligible Pension Income is less than $2,000, the Pension Income Amount will adjust to that amount. Not all income reported on a T4A qualifies as Eligible Pension Income.

This CRA document explains further which income does qualify: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/line-314-pension-income-amount/which-pension-annuity-income-qualifies-pension-income-amount.html