Hi,
in some control centers - especially those with automatic mission creation/patient transport creation - it can happen that more patient transports are created than ambulances are available at that particular time. Based on the urgency of patient transports, this is generally not a problem, but I’m familiar with the practice where resources can then be reserved for a specific mission by the dispatcher, so that when they become available, they automatically appear in the disposition suggestion, allowing them to be alerted further.
So: vehicle is tied up in a mission, patient transport is pending, you decide to reserve this vehicle there → vehicle becomes available (status 8 or 1) → vehicle is already in the resource suggestion for that mission and can be alerted.