UPDATE : We've had further clarification on this situation from NLS. Readers who receive braille materials directly from NLS should be included in the numbers, which means your original Readership & Circulation Report numbers are the correct ones to submit.
Sorry for the confusion!
I will leave the original text of this post in place in case you are curious, but you are free to disregard everything below this line.
NLS has issued a clarification in how they would like the readership numbers for Braille to be calculated. The number should be those patrons who received physical braille materials from your library. It should not include those who are getting braile service exclusively from any of the following sources: direct mail Braille materials from NLS, service from another state, or electronic Braille.
To get the numbers of people who have received braille materials specifically from your library:
Open the Circulation module
Select Circulation Report from the reports>circulation menu
Set the following parameters (see the attached screenshot for an example)
Library ID: select yours, or use All for the entire system
Rec Type: All
Show in Report: (Use the CTRL key to select multiple)