Hi Topsec! You might be getting confused between what is ok for a diabetic, and what diagnoses a person as diabetic.
To diagnose a person as diabetic, the world health organisation says anything above 6.5% diagnoses diabetes, whereas between 5.7% and 6.5% suggests a person is at risk of diabetes. Between 6.0% and 6.5% is seriously at risk (pre-diabetic). Remember, these people are just being diagnosed and probably on a normal high-carb diet.
Once you ARE diagnosed, NICE suggest currently that below 7% is a good result. Different organisations use different levels. WHO say below 6.5% is good control, as do most USA and Canadian diabetes association. I think it's the USA Endocrinologist organisation that suggest below 6% "if safe", meaning if therew is not a risk of the person having hypos (e.g, not on insulin)
Most of us aim to be a lot lower than the 7% that NICE recommend. We like to get nearer to non-diabetic levels, and aim for less than 6%. Some can't get there without undue sacrifices (to the individual) on food (carbohydrate) intake or without unacceptable (to the individual) levels of medication. Generally, the lower the better within limits. 5.5% is the top end of a non-diabetic measurement (they vary from 4.6% to 5.5% on average), so I'd like to get to 5.5 but may not make it!
Don't be overwhelmed by numbers; loads of type 2s don't get below 7. If you do, well done. If you can then graduallyt tweak your diet to get lower a bit at a time, all the better.