These are calls that did not reach the agents because the customer disconnected while in the waiting queue or in the IVR. This could be because they deliberately hung up or lost connection/service (for instance if they called from a mobile device).
These include calls disconnected at any point during the IVR. So you may find that in the reporting dashboard when you filter by ring group the number of calls does not change, since these callers did not yet select an IVR option so they show for all ring groups.
Abandon time is an inbound call metric that captures the time it took customer to hang up before being connected to an agent. The Abandon call timer begins the moment the customer is connected with your call center, and is presented with a Welcome Greeting or IVR.
Additionally, you might want to filter out from abandoned call statistics, such as average abandon time, abandonment rates, calls that are not in the system long enough to be considered as events. This may occur when a caller mistakenly dials your call center, is not interested in dealing with an IVR, or any case where they decided to hang up immediately. To do this, you must configure a Short Abandoned calls threshold for your account.