I try to eat 2 hours before inserting, not less than 2 hrs. Then, calibrate immediately. I used to plug a lot of manual BGs into it, willy nilly. It seemed like an easy way to store the data. But, now I'm really cautious about that because I think its calibrating every time I do that, which makes the sensor read more inaccurate. Now, I don't calibrate unless I've had less than, maybe, 30 points variability in the numbers during the preceding hour. I don't really follow the arrows. I've had really reliable data come out of the thing, but it will read off when your bg raises or lowers rapidly, so you should still check manually, while you learn its quirks.