Evohome app? How to set default 'away' Temps?

15 degree seems excessive to leave our house on when we are away for prolonged periods. It's a new build house, and all pipes are well lagged. 10degrees is a temperature we would prefer..

The info message pops up saying "away sets spend to 15degs as default" which makes me wonder how /if I can change it?

Failing that, how do I set the temperature under the "custom" mode?

Thanks