Installed Make 2017 right now / Windows 7 / 64bit / Swiss-German:
No problem to enter feeds (6’), but inches (6’’) is not possible as shown in the videos (getting startet).
To what do you have the units set in Window>Model Info>Units? If you are working in Architectural–Feet and inches or Decimal inches, or Fractional, you should just be able to type 6’6 for six feet six inches.
it works, don’t enter ''
You could enter " at least on an English install and keyboard arrangement. I don’t know what the arrangement is for your set up. Inches are understood as long as you aren’t using metric units.