Its not a phrase that survives a literal translation (when same!) it has many uses and often people will just throw it in because they are incapable of stringing together a literate sentence, much like "voila" , "et puis voila" "et ben..... donc..... voila", "mais bon"etc.
In the instance quoted above it probably means it was a good meal nonetheless or nevertheless, i.e; despite the crap service, your general air of disinterest or that the cook appeared to be twelve years old, if you get my meaning.
I have also heard it expressed as surprise, i.e if someone scores a lucky point at petanque etc, its something that you pick up when to use without ever really being able to explain how or why and especially translate it.
TizzyLizzy you say that you would like to use it if only you knew what it means, I understand where you are coming from but dependant on where you live it is perhaps not advisable to blindly mimic what you hear as you may well end up sounding like an abruti and people may assume that you are one.