diggerman,
You are stating a definition of "freeboard." That, can be found easily. The "understanding" of freeboard is what has been discussed here in the context that was used (see above),in the language quoted from an RFP. Also see the attached image.
What is your understanding?
On a separate note, I do hope that everyone is employed. These are difficult times for many, not just for engineers, and my understanding of this venues is that these are "intelligent work forums for enginering professionals." With that in mind, you now have, again, the opportunity to help others with your knowledge and expertise.