1. Double click on the dimension.
2. Make sure the "Precision and Tolerance" tab is selected
3. Select the appropriate drop down for either "Hole" or "Shaft"
4. Select a standard fit from the dropdown

You cannot manually select your own arbitrary tolerance for "limits/fits'. All fits use predefined industry standard tolerances.

If you wish to use your own tolerance then you must use "Limits - Stacked" or Limits - Linear".