Update the documentation about what the "more than 35 acres column is doing

[KameronKerger]

Describe the bug
My assumption is that this was used for something. Since it is located by the impervious surfaces columns my assumption is that it is some how related to that burden.

To Reproduce
Steps to reproduce the behavior:

1. Go to '1-communities-list.xlsx'
2. Scroll down to 'BS.'
3. See error

Expected behavior
Document what this is doing, in the TSD or somewhere else.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.