One stretch of a range's history that a consume read moved a consumer past because it was no longer stored: expired by retention, or removed by an operator. Malachi.Broker.read_consume/5 returns one per stretch it stepped over, so the layers above can tell an operator which reader lost data.

The fields:

• range_id - the range being consumed.
• source_range_id - the range whose data was missing: the consumed range itself, or one of its sealed ancestors when the read was still draining the pre-split history.
• from - the source offset the reader was positioned at when the data was found missing.
• offsets - how many offsets were stepped over, or :unknown when an ancestor has no segment left and its end was not recovered after a restart, so only the fact of the skip is known.
• origin - :start when the reader began without a position (a new group, or a child range after a split, which starts over its ancestors), :cursor when it resumed from one it held. Only the second is a reader that fell behind retention.
• source - :self or :ancestor.

The count comes from segment boundaries, never from the gaps between record offsets, so a segment whose offsets are sparse by design is not reported. It counts OFFSETS, not records lost: reading an ancestor delivers only the child's key slice of it, so an ancestor skip is an upper bound on what this child missed (span/1 says :upper_bound).