From the Signatures tab, you can view logs grouped together in a signature. To see the raw log data, click the number in the Count column.
Viewing data in this manner doesn't supply feedback to the logreduce operator; it simply launches a new query adding the details operator that allows you to view the logs grouped under that signature. As you're reviewing the data, you may decide to edit the signature or split the signature, as you see fit.
The LogReduce details query uses the line number of the signature to return these results in a new Search tab.