Readme.md in parallel_tests-4.2.1 vs Readme.md in parallel_tests-4.2.2

@@ -226,10 +226,12 @@
                                      --isolate-n.  Ex.
                                      $ parallel_tests -n 3 . --specify-groups '1_spec.rb,2_spec.rb|3_spec.rb'
                                        Process 1 will contain 1_spec.rb and 2_spec.rb
                                        Process 2 will contain 3_spec.rb
                                        Process 3 will contain all other specs
-        --only-group INT[,INT]
+        --only-group INT[,INT]       Only run the given group numbers. Note that this will force the 'filesize'
+                                     grouping strategy (even when the runtime log is present) unless you explicitly
+                                     set it otherwise via the '-group-by' flag.
     -e, --exec [COMMAND]             execute this code parallel and with ENV['TEST_ENV_NUMBER']
     -o, --test-options '[OPTIONS]'   execute test commands with those options
     -t, --type [TYPE]                test(default) / rspec / cucumber / spinach
         --suffix [PATTERN]           override built in test file pattern (should match suffix):
                                      '_spec.rb$' - matches rspec files