We saw a case where the recovery stats reported `recovered_bytes` greater than `length_in_bytes` for one file:

```
GET /_recovery?detailed

200 OK
...
{
  "name": "_buk.fdt",
  "length_in_bytes": 26891307173,
  "reused": false,
  "recovered_in_bytes": 35324928266,
  "recovered_from_snapshot_in_bytes": 8433621093
}
...
```

NB `35324928266 == 26891307173 + 8433621093`

This causes Elasticsearch to compute a negative value for the reserved space on the target node of this recovery, which prevents stats APIs from working. This appears to be caused by a network-level failure which triggers a retry without first cancelling an ongoing download of a different file with the same name from the snapshot repository.

---

### Workaround

Restart the target node to clear these stats.
x-pack/plugin/snapshot-based-recoveries/src/internalClusterTest/java/org/elasticsearch/xpack/snapshotbasedrecoveries/recovery/SnapshotBasedIndexRecoveryIT.java
.put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
                .put(MergePolicyConfig.INDEX_MERGE_ENABLED, false)
                .put(IndexService.GLOBAL_CHECKPOINT_SYNC_INTERVAL_SETTING.getKey(), "1s")
                .build()
        );
        int numDocs = randomIntBetween(300, 1000);
        indexDocs(indexName, 0, numDocs);
        String repoName = "repo";
        createRepo(repoName, TestRepositoryPlugin.INSTRUMENTED_TYPE);
        createSnapshot(repoName, "snap", Collections.singletonList(indexName));
        assertAcked(client().admin().indices().prepareDelete(indexName).get());
        List<String> restoredIndexDataNodes = internalCluster().startDataOnlyNodes(2);
        RestoreSnapshotResponse restoreSnapshotResponse = client().admin()
            .cluster()
            .prepareRestoreSnapshot(repoName, "snap")
            .setIndices(indexName)
            .setIndexSettings(
                Settings.builder()
                    .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 1)
                    .put("index.routing.allocation.include._name", String.join(",", restoredIndexDataNodes))
            )
            .setWaitForCompletion(true)
            .get();
        RestoreInfo restoreInfo = restoreSnapshotResponse.getRestoreInfo();
        assertThat(restoreInfo.successfulShards(), is(equalTo(restoreInfo.totalShards())));
        ensureGreen(indexName);
        assertDocumentsAreEqual(indexName, numDocs);
        RecoveryState recoveryState = getLatestPeerRecoveryStateForShard(indexName, 0);
        String sourceNode = recoveryState.getSourceNode().getName();
        String targetNode = recoveryState.getTargetNode().getName();