Test coverage as a metric doesn’t say much. It is always a relative figure and if you can’t explain what the scope is of the coverage, it doesn’t say much. This also means that you haven’t covered anything outside the scope….
Conclusion: be very carefull with metrics especially when it acceptance concerned. Acceptance is more about trust, for example: a team which build and tested an airplane, let them do the first flight and if they don’t trust it, you know enough….