Below configuration for Elasticsearch:

```
1 Cluster
1 Node
1 Index
3 Shards (1 Replica shard for each primary, but in UNASSIGNED state as there is only 1 node).
```

I have indexed document and those are spread across 3 Shards(Shard-0, Shard-1,Shard-2).

Term Aggregation I am trying:

```
POST myIndex/_search
{
"query": {"match_all": {}},
"size":0,
"aggs": {
"products": {
"terms": {
"field": "BillToID",
"size": 10,
"shard_size": 11,
"show_term_doc_count_error": true
}
}
}
}
```

Response :-

```
"aggregations" : {
"products" : {
"doc_count_error_upper_bound" : 7,
"sum_other_doc_count" : 12,
"buckets" : [
{
"key" : "ProductA",
"doc_count" : 100,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductC",
"doc_count" : 54,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductZ",
"doc_count" : 52,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductG",
"doc_count" : 47,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductH",
"doc_count" : 44,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductB",
"doc_count" : 43,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductE",
"doc_count" : 31,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductF",
"doc_count" : 19,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductI",
"doc_count" : 11,
"doc_count_error_upper_bound" : 6
},
{
"key" : "ProductJ",
"doc_count" : 9,
"doc_count_error_upper_bound" : 6
}
]
}
}
```

From Defination in Docs Of Per Bucket doc_count_error_upper_bound =

This is calculated by summing the document counts for the last term returned by all shards which did not return the term.

Problem : But When I checked I can see ProductA has been returned by each shard, so why does it shows "doc_count_error_upper_bound" : 6 for ProductA?

Any help is much appreciated:)