Why is there a difference between the amount in my Co-Ownership Approval and your online calculator said I would get?

Our online calculators are provided as a guide and are for illustrative purposes only. 

The maximum amount stated in your Co-Ownership Approval is based on a detailed affordability assessment of your circumstances, based on the evidence you've provided. When we complete our assessment, there may be a difference between the amounts suggested through our calculators, and your actual Co-Ownership Approval.