Printing on Both Sides of page on Samsung Xpress M2875FD

[EdmundX1]

Printing a  Word Document - Windows 10

Samsung Express M2875FD

When I set the printer to print on BOTH SIDES  of the page it  only prints on ONE side? What is wrong and How to Fix?  I am attaching screenshot of the settings

screenshot of settings

[EdmundX1]

Forgot to add: when printing both sides what does 'Flip pages on short edge' and 'Flip pages on long edge'  mean?