Ahhh....duh. I knew I was missing something simple.
Thank you all.
What I think I really need to do is use two calculators:
The one I posted to see how much the 401k account will grow while still contributing to it, and then,
Another separate calculator inputting the amount I got from the above step, to see how much the account will grow to over a certain period without contributions
Basically, I believe there will be a period in my 50s where it's 'possible' I'm not contributing at all anymore but not yet drawing from the funds accumulated in my 401k. I'm kinda trying to work backwards right now to determine how much minimum I need to have in the account before I could potentially stop contributing and be okay with letting it just grow.