Ok, I added a filter called "Remove Specific" for the "TEstss" report in Home > Sample Survey > My Sample Survey.
The intention of this filter is to only remove responses from users who answered "8/5/2010" in the date field.
Question answered
Free form question
Not Answered - Enter a date (Text entry) - Equals to - 8/5/2010 - Text
However, if you apply this filter to the report, you'll see that even though only one person responded with a date of 8/5/2010, the number of respondents listed for the first question drops from 10 to 4. The respondents who left the date field blank were erroneously filtered out.