4.6.3 cbbackupmgr : Some docs missing in backup

Build : 4.6.3-4032

Test Setup :
1 src node (160GB RAM, 40 core CPU)
1 src node (160GB RAM, 40 core CPU)
2 standard buckets
No. of items in default bucket : 288,469,834
No. of items in other bucket : 293,494,288
Total backup size : 852.64GB

Steps :
Load data to both the buckets on src cluster (only creates, no updates, deletes, expiry)
Stop loading after crossing 550M+ items total
Take full backup on dest cluster node (I had to do this because dest cluster node had more disk space than src cluster node)
Do a cbbackupmgr list and compare items in the backup vs the no. of items on src cluster.

Issue : The no. of items in the backup for default bucket is 288469453, which is 381 items less.

Restore worked fine on the dest cluster, all items in the backup were restored.

cbbackupmgr list output
root@ip-172-31-29-37:/opt/couchbase/bin# ./cbbackupmgr list -a /backup -r backup
Size Items Name
852.64GB - + backup
852.64GB - + 2017-06-20T17_21_46.290462185Z
379.19GB - + default
335B 0 bucket-config.json
379.19GB 288469453 + data
11.83GB 9015346 shard_0.fdb
11.89GB 9014339 shard_1.fdb
11.76GB 9014713 shard_10.fdb
11.89GB 9014744 shard_11.fdb
11.75GB 9014732 shard_12.fdb
11.86GB 9014884 shard_13.fdb
11.83GB 9015101 shard_14.fdb
11.82GB 9014380 shard_15.fdb
11.85GB 9014739 shard_16.fdb
11.79GB 9014454 shard_17.fdb
11.81GB 9014795 shard_18.fdb
12.03GB 9014073 shard_19.fdb
11.87GB 9014597 shard_2.fdb
11.85GB 9014201 shard_20.fdb
11.80GB 9014632 shard_21.fdb
11.77GB 9014352 shard_22.fdb
11.84GB 9014708 shard_23.fdb
12.04GB 9014737 shard_24.fdb
11.81GB 9014729 shard_25.fdb
11.82GB 9014361 shard_26.fdb
11.82GB 9015198 shard_27.fdb
11.99GB 9015128 shard_28.fdb
11.80GB 9014453 shard_29.fdb
11.87GB 9014635 shard_3.fdb
11.84GB 9014468 shard_30.fdb
11.88GB 9014582 shard_31.fdb
11.86GB 9014555 shard_4.fdb
11.95GB 9014959 shard_5.fdb
11.80GB 9014192 shard_6.fdb
11.83GB 9015246 shard_7.fdb
11.81GB 9014287 shard_8.fdb
11.85GB 9015133 shard_9.fdb
2B 0 full-text.json
4B 0 gsi.json
2B 0 views.json
473.45GB - + other
333B 0 bucket-config.json
473.45GB 293494288 + data
14.65GB 9171364 shard_0.fdb
15.26GB 9172154 shard_1.fdb
14.74GB 9171877 shard_10.fdb
14.73GB 9171435 shard_11.fdb
14.82GB 9171572 shard_12.fdb
14.74GB 9171762 shard_13.fdb
14.76GB 9170912 shard_14.fdb
14.74GB 9172362 shard_15.fdb
15.20GB 9171204 shard_16.fdb
14.80GB 9171724 shard_17.fdb
14.69GB 9171245 shard_18.fdb
14.71GB 9172022 shard_19.fdb
14.72GB 9171999 shard_2.fdb
14.75GB 9171996 shard_20.fdb
14.80GB 9171225 shard_21.fdb
14.73GB 9171835 shard_22.fdb
14.73GB 9171097 shard_23.fdb
14.69GB 9172086 shard_24.fdb
14.80GB 9171369 shard_25.fdb
14.76GB 9172155 shard_26.fdb
14.72GB 9171678 shard_27.fdb
14.71GB 9171510 shard_28.fdb
15.24GB 9172178 shard_29.fdb
14.72GB 9171577 shard_3.fdb
14.71GB 9171431 shard_30.fdb
14.70GB 9172067 shard_31.fdb
14.74GB 9171593 shard_4.fdb
15.18GB 9171800 shard_5.fdb
14.79GB 9172598 shard_6.fdb
14.71GB 9171346 shard_7.fdb
14.68GB 9172310 shard_8.fdb
14.75GB 9170805 shard_9.fdb
2B 0 full-text.json
4B 0 gsi.json
2B 0 views.json