You have to remember that the 30 day average on your meter is only the average of the readings you've taken.
Sorry if that's obvious, but say you only took a waking reading and not +2hrs after meals, then all the readings in the meter would be low, so your 30day average would also be low.
To be really indicative, you need to have a solid mixture of before, +1hr and +2hr readings across the day (as many of us are more tolerant of carbs at differing times of the day) and then keep this testing going for a month. The trouble is you'll use an awful lot of test strips.
I don't want to discourage you - 5.1% would be fantastic - but be aware of the data you're basing it on.