title: Arena Simulation (Rockwell) - steady -state / model verification
body: <p>how can I verify that my Arena model (serial supply chain) is within a steady-stated (closed) system? 
  I got from the simulation reports: number in (614 entities), number out (602 entities) and WIP (average inventory) of around 12.67. Can this used as a proof? 
  because this is according to my understanding: 614 total entities enter the model, within are on avg 12.67 and until the end of the simulation leave about 602.  Is this right? I couldnt find anything in Kelton / Altiok etc</p>