MongoDB Shard distribution issue
As per MongoDB documentation here which prints the data distribution statistics for a sharded collection. You must call the getShardDistribution() method on a sharded collection, as in the following example:

db.myShardedCollection.getShardDistribution()


In the following example, the collection has two shards. The output displays both the individual shard distribution information as well the total shard distribution:

Shard &lt;shard-a&gt; at &lt;host-a&gt;
 data : &lt;size-a&gt; docs : &lt;count-a&gt; chunks : &lt;number of chunks-a&gt;
 estimated data per chunk : &lt;size-a&gt;/&lt;number of chunks-a&gt;
 estimated docs per chunk : &lt;count-a&gt;/&lt;number of chunks-a&gt;

Shard &lt;shard-b&gt; at &lt;host-b&gt;
 data : &lt;size-b&gt; docs : &lt;count-b&gt; chunks : &lt;number of chunks-b&gt;
 estimated data per chunk : &lt;size-b&gt;/&lt;number of chunks-b&gt;
 estimated docs per chunk : &lt;count-b&gt;/&lt;number of chunks-b&gt;

Totals
 data : &lt;stats.size&gt; docs : &lt;stats.count&gt; chunks : &lt;calc total chunks&gt;
 Shard &lt;shard-a&gt; contains  &lt;estDataPercent-a&gt;% data, &lt;estDocPercent-a&gt;% docs in cluster, avg obj size on shard : stats.shards[ &lt;shard-a&gt; ].avgObjSize
 Shard &lt;shard-b&gt; contains  &lt;estDataPercent-b&gt;% data, &lt;estDocPercent-b&gt;% docs in cluster, avg obj size on shard : stats.shards[ &lt;shard-b&gt; ].avgObjSize


For your further ref here, here