DOCSP-33577 progress output clarification (#174)

* DOCSP-33577 progress output clarification

* Fixes per Ian

* Fixes per Dave Rolsky

* Fixes per Ashley

Co-authored-by: Ashley Brown <98361885+mdb-ashley@users.noreply.github.com>

---------

Co-authored-by: Ashley Brown <98361885+mdb-ashley@users.noreply.github.com>

Author: kennethdyer

source/includes/api/tables/progress-response.rst

@@ -41,7 +41,7 @@
    * - ``lagTimeSeconds``
      - integer
      - Time in seconds between the last applied event and time of the
-       current latest event.
+       current latest event for this instance of ``mongosync``.
 
    * - ``collectionCopy``
      - object
@@ -51,13 +51,19 @@
    * - ``collectionCopy``
        ``.estimatedTotalBytes``
      - integer
-     - Estimated total number of bytes to be copied.
+     - Estimated total number of bytes to be copied globally by all ``mongosync``
+       instances.
 
    * - ``collectionCopy``
        ``.estimatedCopiedBytes``
      - integer
      - Estimated number of bytes which have been copied to the
-       destination cluster.
+       destination cluster by this ``mongosync`` instance. 
+       
+       To calculate the total estimated progress as a percentage, add the value
+       of the ``estimatedCopiedBytes`` field for each ``mongosync`` instance
+       and divide the result by the value of the ``estimatedTotalBytes`` field
+       . Then, multiply the result by 100.
 
    * - ``directionMapping``
      - object