How does ANSYS calculate safety factor in backend

I am working on a project
I have designed a prosthetic leg and performed analysis in ANSYS Software, I got the values total deformation, stress and safety factor by applying some load on prosthetic leg
I want to prove that the values which I obtain in ANSYS are correct by calculating same values by hand so I want to know how ANSYS Software calculate safety factor in backend so that I can use same formula to get the value when I do by hand
Thankyou