It can be used in a variety of ways as a way of putting a certain emphasis on the statement. In this context the sentence would translate to: "It is good enough, really"
I found this explanation in a Danish grammar:
"da, dog, jo, lige, nemlig, nok, nu, sgu, skam, vel, vist: These are unstressed modal adverbs expressing the speaker’s attitude to what (s)he is saying, and it is difficult to give exact rules for their idiomatic use. "
"it really is good enough" apparently needs to be added, as it took 'it is really good enough' which is the same thing.
Why is a translation of "it seems good enough" wrong? Earlier "det er da ikke så dårligt" was translated as "it does not seem so bad", so it would seem to me that "det er da" might mean "it seems" or something similar. What is the context required for this interpretation?
Because for the english language "da" depends on context. not really in german though, were it would be for "det er da ikke så dårligt": "das ist doch nicht so schlecht" and for "det er da godt nok" it is "das ist doch gut genug". but "da" cannot be easily translated like that for english. it depends on context very much... i wish i could give a better answer.
If I say "It should be good enough" it carries conviction that something really is good enough. I think my suggestion should be accepted.
"It should be good enough" sounds like you're not really sure if it suffices. But with the addition of da in the Danish sentence you're trying to sound convincing, because you know it's good enough.