Rejection Rate defined in a study Model but output getting is incorrect

Hello,

I am trying one scenario considering 50% rejection rate at two machines in a line but the output count i'm getting is not correct.

Scenario: I have considered 1000 Products to be produced as per below model, 50% rejection Rate is defined at machine 2 so 500 good products should go through the in-line conveyor and 500 products should go the rework at machine 3 where again 50% rejection rate is defined so 250 out of 500 should go to in-line conveyor and remaining should go to storage (buffer) defined.

Below are the results:

So the output as per expectation should be 750 but after running this scenario the output showing is 740. 

I have not sure what I am missing here? Could someone please help me here?