If your company forces employees that leave the premises to close their current time card and create a new time card when they return, then what the employees should do when they leave the premises is to use the “End Shift” button in the Shop Floor Insight Web Client.
This will automatically clock off the employee from any currently open activity and it will also close the current time card. The next time this very same employee scans his/her employee badge, a brand new time card will be created. Please note that a new time card will be created regardless if the employee just ended his shift 5 min ago or last week.
Therefore upon their return from lunch, the moment an employee scans their employee badge, this will automatically create a brand new time card.
As for the setting you are alluding to – the “Hours before close” setting found on the Shop Floor Setup page: This setting will come into play only whenever the employee scans his/her employee badge and there is an open time card already. If the “inactivity” period of time is larger than the value in this setting, then the open time card will automatically close, and a new one will be created for this employee. If the inactivity period is less than the value, then the open time card will be used. If there is no open time card, a new one will be created.
As I understand it, this setting will not change anything for you in this context of employees going to lunch.