To be counted as congested, a vessel needs to be in an anchorage polygon for more than 3 hours.
There are two counts for the Oceanbolt congestion metrics.
live count - i.e. how many vessels are currently waiting
daily count - is used to generate a time series of historical counts. The daily count is captured at 00:00 UTC.
Waiting times are calculated from the arrival time at anchorage, but only include vessels that are actually counted as congested.