It is usually best to connect Start Points to Queues first, otherwise, if two Work Items arrive in quick succession, and the Activity you have routed them to cannot accept them (if it is busy) then the Work Item will be thrown away, and will not enter your simulation. Sometimes you might want this: if, for example, you want to simulate customers being lost because a phone system is busy.
If you want to count the work-items being lost connect the work-entry point to a work-exit or queue. Set the Routing Out discipline from the work-entry point to priority. Make sure that the preferred route is listed first.