Start by reading the report rather than reacting to the number. An appraiser carrying a designation from the Appraisal Institute of Canada lists the comparable sales used and the adjustments applied, and errors do happen: a missed finished basement, a comparable from a weaker pocket of the city, square footage taken from an old file. A written reconsideration of value with better comparables attached is a real remedy and it is often the fastest one.
If the value stands, the arithmetic is simple. A lender approving 80 percent of a value that came in $10,000 light leaves an $8,000 hole you either fill in cash or negotiate away. With default insurance in play through CMHC, Sagen or Canada Guaranty, the insurer is looking at the same appraised figure, and Saskatchewan charges provincial sales tax on that premium in cash on possession day.
The seller has an interest in solving this too, because the next buyer's lender will likely order an appraisal and reach a similar number. Meeting in the middle is common. What prevents the situation entirely is pricing off documented improvements rather than hope, which is what Joel Dyck's hand-reviewed valuation is built to do.