@Override
    public CompletableFuture<FetchResult> fetch(FetchContext context, long startOffset, long endOffset, int maxBytesHint) {
        long fixedStartOffset = Utils.max(startOffset, 0);
        return stream.fetch(context, startOffsetInStream + fixedStartOffset, startOffsetInStream + endOffset, maxBytesHint)
                .thenApply(FetchResultWrapper::new);
    }
the real start offset of this segment in the stream.
core/src/main/scala/kafka/log/streamaspect/DefaultElasticStreamSlice.java