If you elect for your monthly contractual payments to shorten your term, the impact of this will show on the dashboard, on the financial wellbeing section.
As you make overpayments, this will reduce the amount of time left on your mortgage.
If the dashboard shows that you have saved 1 month off of your mortgage, this means one fewer monthly payment you need to make at the end of your mortgage. If you take hours off of your mortgage, this will reduce your final mortgage payment accordingly.