Your property is assessed by the municipality's assessment service provider (usually but not necessarily the Saskatchewan Assessment Management Agency) who calculates a value for tax purposes.
A provincially established percentage is applied to this value - this is called your taxable assessment.
The municipal council adopts a budget outlining expected expenditures and revenues, including the amount to be generated by property taxation. Then, the council establishes the municipal tax rate (or uniform mill rate) expressed as a mill, by dividing the amount of tax revenue it requires by the total taxable assessment, and multiplying that number by 1,000.