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.