My understanding is a 0.5 means a few seconds of lucidity.
Prelucid isn’t lucid, so those don’t count.
If you go to the first page of the thread, there’s a link to previous discussion of the rules.
For myself, I’m noticing more glimpses lately, but the lucid moments I’ve gotten in the last week were so brief, I’d almost rather count them as 0.25 each. And this morning I had another brush with lucidity, which I’m not going to count here, but I do feel encouraged.