Fix #20 #25, Add requirements rationale and clarify event message limit requirement

Checklist (Please check before submitting)

[x] I reviewed the Contributing Guide.
[x] I signed and emailed the appropriate Contributor License agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

Testing performed NA - requirements updates only

Expected behavior changes None

System(s) tested on NA

Additional context None

Third party code None

Contributor Info - All information REQUIRED for consideration of pull request Jacob Hageman - NASA/GSFC

nasa / LC