Docs.count is diffenet when I twice post data to elasticsearch

[kiddingl]

elaticsearch: 6.3.1
os: centos7
kernel: 3.10

I run the shell command:

curl -H 'Content-Type: application/x-ndjson' -XPOST 'localhost:9202/shakespeare/doc/_bulk?pretty' --data-binary @shakespeare_6.0.json

The end of command resaults

About 111396 documents was stored into elasticsearch

Run the shell command and observed docs.count

curl -XGET 127.0.0.1:9201/_cat/indices?v

The resault of command through _cat API:

docs.count is 111395, I don't know why lost one

Execute top command again

curl -H 'Content-Type: application/x-ndjson' -XPOST 'localhost:9202/shakespeare/doc/_bulk?pretty' --data-binary @shakespeare_6.0.json

The end of command resaults

No problem

The resault of command through _cat API

docs.count is 111396 which is right, I am confused , I don't known why command is excuted twice?