On the staff details page there is a Settings module which has a setting "Notify Attendance Approval".
Ticking the Notify Attendance Approval means that when the shift clockin or clockout times are approved on the worker's timesheet then an alert is sent to the app to let the worker know.
The attendance clockin/clockout time approval notification can be turned off by unticking this setting.
Please note, when rejecting the time an alert is still sent to the app with the reason provided. Rejected reasons are always sent to the worker regardless of this setting.
This screenshot below shows the worker's app notifications - the rejected message will be received by the worker regardless of whether "Notify Attendance Approval" is ticked or not.