This reports whether this specific call requested the X.25 fast select facility, which lets a small amount of data ride along with the call-setup request itself rather than waiting for the call to fully establish first. An admin checks this per call to understand why a particular short-lived call's data appeared to arrive unusually quickly, since fast-select calls skip the normal call-establishment data-transfer delay. For example, a call showing fastSelect combined with a very short connection-up time would be consistent with a single-transaction query-response exchange rather than a sustained session.