Ron,
First of all, sorry about the delay in answering this. It is so great to hear from TU Delft where I used to go when I first started teaching. Specifically it was YES Delft and many great memories.
With regard to your question, this is a very common point that I need to clarify so let me do it here in writing.
First there is the BHM (Beach Head Market) TAM which should be big enough to be attractive BUT ALSO SMALL ENOUGH to be something you can do with a relatively small amount of resources and in a reasonable period of time. This BHM TAM does not represent the total potential for your business but simply the market revenue opportunity (at 100%) of your first market. By the way, there are limits to the value of simply the annual revenue potential and I have a robust discussion of this in the Disciplined Entrepreneurship Workbook which you should read as well.
So the BHM TAM should be big enough to be interesting to allow you to build up credibility and critical mass to then expand into additional markets with momentum and some increased competitive advantage gained from the success in your BHM. It would also be nice to get to cash flow positive too especially in areas where it is harder or more expensive to raise money to expand. You do not want your BHM TAM to be so big as be overwhelming or create lack of focus. Specifically, when students say there BHM TAM is $2 Billion in annual revenue (annual revenue is the right units), I immediately say that is too big. Why? Because it is almost a sure things that 2-3 people, or even 20-30 people, will be able to successfully win such a large market to start. It is like boiling the ocean. Rome was not built in a day. One step at a time. 
Even the great Jeff Bezos, with visions of world domination that he is on his way to seemingly achieving, started with a very small BHM TAM of books. See  https://www.d-eship.com/articles/bezos-focus-on-books-greatest-execution-of-beachhead-marketing/
Now that is the BHM TAM which an entrepreneur should know but the entrepreneurship should also know their overall business TAM. That is what is the total market opportunity for the business (in revenue per year) once it fully expands into all the markets. This is the sum of all the TAMs from the BHM TAM to all the follow on markets identified in Step 14. This shows your company full impact and greatness when it is fully successful. This is the number that investors are usually interested in. How big can this be? This could very well be billions of dollars and be comfortable sharing this with people if you have done the work enough to back it up with step 14 but also realize that the path to greatness starts with the first step. You have to have a vision of greatness but before you expand you have to successfully land and win that first beach head market like Bezos did. There would be no Amazon today without the focus on books to start and to build up the confidence, momentum and critical mass they got in the beach head market … but he was also always selling the vision to employees, investors and anyone who would listen of being the “go to” place for ecommerce in the long term.
Does this answer your question Ron?

It does. So we need to always specify which TAM we are discussing. TAM BHM, Tam follow-on market 1, TAM follow-on market 2, TAM total business.
Or just start talking about Market Sizes and specify :).