Something has been done adequately when basic requirements are fulfilled. Passing your driver's test probably means you parallel parked adequately; if not, you may have knocked over some cones.
The adverb adequately is a synonym for sufficiently, or suitably. If you've adequately fulfilled your course requirements, you're probably neither the best nor the worst student in the class. But you've definitely done well enough that you can pass — so doing something adequately is generally a positive thing, unless you're an overachiever, in which case you might not like that description at all!