The required distribution is the account balance divided by the IRS Uniform Lifetime factor for the age you enter. This tool uses the published factors for ages 72 through 120. Age 73 uses 26.5. The page does not use the Joint Life table.
A $400,000 balance at age 73, factor 26.5, has a required distribution of $15,094.34. A larger balance at the same age raises the distribution in proportion. The factor gets smaller as age increases, so the same balance requires a larger distribution later.
This is the US IRA required minimum distribution. It is not a Canadian RRIF minimum. It does not know your beneficiary’s age, and it does not calculate the income tax on the withdrawal.