No, you cannot Check Out of the Job on the mobile app if you have Checked in to the Job from Salesforce.

As of now, you should Check-Out from Salesforce if you checked in from Salesforce. And if you are using the PK4 TimeTracker Mobile app then you should Check-In and Check-Out from the Mobile app only.

We are currently working on the process to give an option to Check-In from Salesforce and Check-Out from the device or vice-versa, and once it is implemented you can Check-In to the Job from Salesforce and Check out from the device.