When you let tado° automatically determine the optimum Away Temperature, it lowers the temperature depending on the characteristics of your building and how far you are from your home. But tado° lowers the temperature only so much that it is able to raise the temperature to your scheduled temperature by the time you get home, i.e. the further you are, the lower the Away Temperature would be as tado° would have more time to preheat your home.
If you work very close to your home, tado° would not have much time to preheat, so it may not lower the temperature as much as you may like whilst you are away. In this case, you can disable the Preheat Before Arrival and set a Minimum Away Temperature that fits your needs. Simply go to the Away tab of the Smart Schedule, move the Preheat Before Arrival slider to OFF and choose the Minimum Away Temperature that you would like tado° to let your home cool down to, when nobody is home.