This means that the displayed content must be in the bottom N results of the value specified. This could be used on a numeric column such as Height.
Using the Height column, this means the displayed content will be among the 11 smallest scaffolds.
Note that, if multiple values are the same value then they will be counted as the same position. For instance, the three scaffolds 5 meters high will fill positions 2-3 and the next scaffold 6 meters high will fill positions 4-5.
Also note that any empty values will have a ranking of 0 but will still be included among the bottom-ranked scaffolds.