DOCS-10359 - Adding point about negative values for printSlaveReplicationInfo()

Author: jeff-allen-mongo

source/reference/method/rs.printSlaveReplicationInfo.txt

@@ -41,3 +41,19 @@ A :ref:`delayed member <replica-set-delayed-members>` may show as ``0``
 seconds behind the primary when the inactivity period on the primary is
 greater than the :rsconf:`members[n].slaveDelay`
 value.
+
+A member may show a negative time value behind the primary when
+:method:`rs.printSlaveReplicationInfo()` is called. This behavior is
+expected if the method is called after a secondary replicates a write
+following a period of inactivity, but before it has received a
+heartbeat from the primary with its latest optime.
+
+.. note::
+
+   The lag reported by secondaries may not be representative of cluster
+   health. Negative values do not indicate that the secondary is ahead
+   of the primary.
+
+   For the most up-to-date information on your replica set, it is
+   generally advisable to run
+   :method:`rs.printSlaveReplicationInfo()` on the primary.