That's CAS latency. To calculate the latency of a timing you divide the timing itself by the clock frequency of your sticks. For example, DDR4-4000 CL14 is running at 2000MHz = 2GHz, so the CAS latency is 14/2 = 7ns.
My Garmin (255s) is pretty inaccurate when it comes to sleep. It often mistakes REM for awake and vice versa. Honestly, nowadays I only wear it for my runs. Even if it was accurate, I can just tell by feel. All the metrics such as sleep, resting HR and HRV are pretty bad compared to your nervous system.
The metrics aren't really actionable either. I got a bad night of sleep, so what? I know it. I have low HRV because I drank alcohol/over-trained/am ill. I don’t need a watch to tell me that. I know it.
It’s just collecting data for the sake of collecting data.
I used it to read some webnovels a few months ago. It's much better than other machine translators (like google or deepl) but it's a bit tedious to use because of the character limit.