Side-note: You don't have to denote the unit for Duration. You construct it from milliseconds, but then it's unitless and you decide where you use it in what unit you want the value. So, Duration is very cool and I would recommend using it for LRC_START_THRESHOLD as well.
Expanding on this further, but the best kind of documentation for what a value represents is its type. Since all of these are duration-related, I would even go as far as using only Duration types for these. The values in Hz (aka n/sec) can be inversed to turn them into Durations (which happens below them to create REFRESH_DURATION and METADATA_REFRESH_DURATION which, despite their names, are actually intervals from what I can tell).