Working hours are defined on the working rota in the work profile.
If there are other employees within the same Work Profile as the employee you need to change, you'll need to create a new Work Profile for them.
To do this go to Leave > Admin & Config > Work Profiles > Create.
Top Tip: You can use the duplicate work profile tool and just change the working rota to keep the rest of the settings the same.
To change the working hours, go to the Work Profile > Leave Settings > Working Rota. Here you can change the working hours in a day or select the "Modify days individually?" button at the bottom of the working rota, to add in specific times.
It's worth noting that once you've changed the working hours, you may need to go and update past leave requests to ensure they are calculating the correct deduction based on the new working hours.