If you see the error as below and are unable to install the PK4 TimeTracker application, it is because the Enhanced Folder sharing for Reports and Dashboards are not enabled in your Salesforce org and this is a known issue in Salesforce.

There are problems that prevent this package from being installed.
An unexpected error occurred. Please include this ErrorId if you contact support: 108345855-16255 (-1818293276) 

You can enable the Reports and Dashboard folders in your Salesforce org by following the instructions here. Once the Enhanced folders are enabled in your org, you can install the PK4 TimeTracker application.