If only a single configuration is used then use a fixed value. If a new configuration is introduced then use the next higher flag value. Undefined or no comment. Clear, easily filtered data, with little or no noise. Clear data with a significant amount of noise, or weak data with little noise.
Data are certainly present, but filtering is difficult.
Value '1' for this 1997 revision. UTC in units of 0.1 microseconds. Two-way value in picoseconds.