When updating a field description from View Field Configuraiton, you are returned to the View Custom Fields screen.

If you edit a field description using the Edit link in the View Field Configuraiton screen, the following happens:
Cancel --> returns you to the View Field Configuraiton screen
Update --> updates the description and takes you to the View Custom Fields screen

If you update a field from the View Field Configuraiton screen , you shold return to that screen.