Segment is used to briefly give details about the situation. There is no need to ramble on and on, but make sure that you give the decision makers enough information so react appropriately. (http://www.hodu.com/memo-writing.shtml)
However, it is best not to have to use a summary segment. Remember that in a memo, less is more.
the context and problem, and the specific assignment or task
In the discussion segment, give details about the problem, Don't ramble on incessantly, but do give enough information for decision makers to resolve the problem. Describe the task or assignment with details that support your opening paragraph (problem).
you want to separate a summary segment