Xiaomi's MiBand sleep tracking is inaccurate for daytime naps

The band seems to be programmed to only accept night sleep. My daytime naps (around 4 hours of sleep) never get counted.

It's step counter seems to be a bit more accurate, but only take it as a rough estimate. The first day I used it it gave me 2000 steps more than usual, despite the fact that I walked LESS than the following days. I guess it may have counted some steps from the time it was locked and unwilling to pair with any device - see my last post.