This is possibly irrelevant as I'm a T1 on mixed insulin, but yesterday I had the best day ever with my bg ranging from 5.2 to 6.8. Don't know how I did it !!!!! Today they're all over the place going from 5.6 to 9.6. I think this is the nature of the beast. As someone else said, Diabetes is not a science, more like a black art at times. I just tend to take one day at a time, some are good, some ok and others a downright shambles. Some forum members keep a very tight control on their bg levels, but I tend to take a more relaxed attitude and strive to keep my levels between no less than 5 and no more than 9. Try not to analise unusual results too much as you'll drive yourself crazy, I did and I gave up as I now accept my body is not a machine and can do strange things that I don't expect.
Congratulations though on your level bg results today. Don't be disappointed if they range from 4.1 to 7.5 tomorrow, they're still good results.