The only well defined code is the “slow blink” (1s on, 1s off) in the bootloader. In application mode, the LED simply turns on when the meter’s processor is awake. So in hibernation mode, you see it come on for a short time once every 10 seconds or so. When connected and sampling, you’ll see it blink at different rates depending on the sampling parameters. And in logging, you’ll see it come on every time the meter wakes up to take a sample and write to SD.
I hope this helps. Is there a specific behavior I can help you understand?