@Override
        public ConvertedRecords<? extends Records> downConvert(byte toMagic, long firstOffset, Time time) {
            return RecordsUtil.downConvert(batches(), toMagic, firstOffset, time);
        }
Return the largest timestamp of the messages after a given offset

@param startOffset The starting offset.
@return The largest timestamp of the messages after the given position.
core/src/main/scala/kafka/log/streamaspect/ElasticLogFileRecords.java