DOCS-9127: clarifies that arbs make for uneven num of voting members

Author: schmalliso

source/core/replica-set-arbiter.txt

@@ -18,14 +18,14 @@ Replica Set Arbiter
 An arbiter does **not** have a copy of data set and **cannot** become
 a primary. Replica sets may have arbiters to add a vote in
 :ref:`elections of for primary <replica-set-elections>`. Arbiters
-*always* have exactly ``1`` vote election, and thus
-allow replica sets to have an uneven number of members, without the
-overhead of a member that replicates data.
+*always* have exactly ``1`` election vote, and thus
+allow replica sets to have an uneven number of voting members without the
+overhead of an additional member that replicates data.
 
 .. important:: Do not run an arbiter on systems that also host the
    primary or the secondary members of the replica set.
 
-Only add an arbiter to sets with even numbers of members. If you add
+Only add an arbiter to sets with even numbers of voting members. If you add
 an arbiter to a set with an odd number of members, the set may suffer
 from tied :term:`elections <election>`. To add an arbiter, see
 :doc:`/tutorial/add-replica-set-arbiter`.