A 27.8 mmol/L equates to an A1c of ~19.1 or slightly over ~500 mg/dl. To answer your question, this is not good. As for a standard try to get your blood sugar below 140 mg/dl or 7.8 mmol/L for now and set your goal for a normal blood sugar, see the normal blood sugar
link. Read the first three threads in the Type 2 Section. They will help you a lot.