number of vb_replica_curr_items isn't equal to number of curr_items in Magma YCSB runs

In our Magma YCSB runs, we saw this issue happened frequently. The number of vb_replica_curr_items isn't equal to the number of curr_items.
11:36:14 2020-07-16T18:36:14 [INFO] curr_items: 100000000, replica_curr_items: 99999997
Here is an example run.

Build: 7.0.0-2581

Job: http://perf.jenkins.couchbase.com/job/magma-nvme-ycsb/203/

Logs:

https://s3.amazonaws.com/bugdb/jira/qe/collectinfo-2020-07-16T182630-ns_1%40172.23.100.135.zip

https://s3.amazonaws.com/bugdb/jira/qe/collectinfo-2020-07-16T182630-ns_1%40172.23.100.136.zip

https://s3.amazonaws.com/bugdb/jira/qe/collectinfo-2020-07-16T182630-ns_1%40172.23.100.137.zip

https://s3.amazonaws.com/bugdb/jira/qe/collectinfo-2020-07-16T182630-ns_1%40172.23.100.138.zip