Details on VF2013 Update 5 Fix (DPD200256609)

I was wondering if someone could post more details on the item fixed in Visual Fortran 2013 Update 5? 

The issue is: DPD200256609 and the title is: "Different answers with optimization and debug"

We use Fortran as a core part of our system and I was wondering what would cause these differences so that we can recommend our team updating to Update 5. 

Thank you!