Q:

ElasticSearch memory useage in kibana doesn't match Windows

I'm running ElasticSearch 6.3.1 with Kibana on a Windows 2012 R2 server with 16g ram.   Windows is reporting my ElasticSearch service is using 12g of ram but in Kibana I only see maybe 8gb allocated/used.   What is using the other 4gb of ram? 
I only have one node at the moment.   Currently I have the JVM heap configured to use 7gb based on the ElasticSearch recommended ram configuration of 50% for heap and 50% for Lucene to use. 
In Kibana monitoring, I show 7g available for the heap, and maybe another 500mb for lucene index memory. 

A:

There are two main types of memory usage: working set and private working set.  The private working set is the amount of memory used by a process that cannot be shared among other processes, while working set includes the memory shared by other processes.  Source
Resource Monitor is showing Elasticsearch is using about 8 GB of memory, the 12 GB working set shown also includes memory shared by other processes.