These are the NICE guidance targets used by the NHS
Non diabetic before meals 4 to 5.9, after 2 hours under 7.8
Type 2 before meals 4 to 7, after 2 hours under 8.5.
However, the general feeling is these targets are too generous so many of us aim for under 7.8 at any time after meals and under 6 before meals. Many others aim for less than that. Some people see a lot of 4's, but not many see 3's, and for some people under 4 can make them feel poorly.
Apparently, our lowest readings are normally before our main evening meal, and our morning fasting is the most stubborn one to control.
It is best to set your own targets, and not a wise idea to compare your readings with others. We are all at different stages of controlling this disease, we all have different metabolisms, and some have different types of medication whilst others have no meds at all.