Not all data return in aggs

Hi, I have a query with aggs by name. In the index I have about a 26800 unique names, but in aggs I have returned less then 20 000 of items. Why other items are missed?

Can you give some more information about what you are doing? And also, show the query that you are running on Elasticsearch to get these aggregations?

Yes, here the query:
curl-XPOST '127.0.0.1:9200/index1/_search?search_type=count&pretty=true' -d
{
"from": 0,
"size": 0,
"aggs": {
"top-tags": {
"terms": {
"field": "sld",
"size": 0
},
"aggs": {
"top_tag_hits": {
"top_hits": {
"size": 1
}
}
}
}
}
}

sld it is the name for aggs. query return about 17K of buckets. But in the index must be 25K unique names. Maybe Elastic have some aggs limitation in core level? or limit size for response message?