Update deploy-oob.md

READMES/devops/deploy-oob.md

@@ -142,3 +142,14 @@ Chances are that any situation serious enough to require an out-of-band deploy w
 To create the postmortem, follow the procedure [here](https://github.com/department-of-veterans-affairs/va.gov-team-sensitive/tree/master/Postmortems). Note that this involves a pull request and review process. Don't just create it in `master` :slightly_smiling_face:
 
 Remember that the purpose of a postmortem is to determine the root causes – the deficits in processes and tools – that made this situation possible, and reduce the likelihood of it happening again. It is not to assign blame, express guilt, etc.
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+#### Communicating Impact
+
+Take extra care in how you report the impact. Use actual, quantifiable figures, statistics, and graphs if you have them. Be sure to communicate the normal, background figures for comparison: the background error rate, the number of users total and the users who _weren't_ affected by the issue, etc. It's difficult to understand or convey actual impact without an understanding of the normal situation. 
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+If you can't readily access this information:
+- acknowledge that problem in the postmortem document
+- open and prioritize tickets to address
+- list these among your followup actions in the postmortem document
+
+Ultimately, someone reading your postmortem should be able to come away with a good understanding of the severity of the issue and its impacts on direct users of the CMS, stakeholders within the system, and the Veteran community.