How many of the 9 factors have current data. If a critical factor (El Nino, water, heat, flood, cyclone/wind, sea state) is missing or stale, the overall level is Unknown.
Koh Samui watch
Missing data is never read as "safe". The engine checks each factor:
No data (the source did not answer, or nothing was collected): the factor level is unknown.
Stale data that would read 0: also unknown (old calm data cannot prove it is calm now).
The six critical factors are enso, water, heat, flood, cyclone_wind and sea_state: each can on its own move the level to Act or Leave, or (El Nino) sets the background of the season. If any is missing or stale, the overall level is Unknown, and the page shows "at least ..." computed from the factors that do have data.
Air, marine heat and news are secondary: if they are missing, the level is still computed, and the headline says which ones lack data.