In another forum Treesize Free was recommended and seems to have revealed the source of the discrepancy in sizes being reported by Explorer. Treesize Free was installed and shows a folder with 3.2 GB of of 55 files that are various system files. Adding that 3.2 GB to the 1.7 GB for all files hows in Explorer gives roughly the same total Explorer shows for this partition. Why does Explorer not shows the 3.2 GB folder with 55 files especially considering I have Explorer set to show hidden files?
Anyway it appears I may have to repartition the drive creating a larger partition for that first volume and restore an image of that partition to the resized larger partition on volume 1 of the drive.. I'm glad Treesize Free helped resolve the problem without which the problem may have remained unresolved. This weekend looking at an external usb drive I noticed similar discrepancies in drive space versus files data size which showed 148 GB used drive space while files data size showed 97 GB. I hope Treesize Free will help resolve that discrepancy too.