The "Group by" step simply counts the number of rows. Note that if you want to do this from a database source, you can simply launch a SQL statement like this to get the answer right away: SELECT count(*)
Now that we have a result row with a single value, how do we obtain this value in the job? Well, we can use the "Evaluation" job entry.
The code is as follows:
var nrRows = rows\[0\].getInteger("nr", \ -1)
nrRows > 100
As you can see we provide you with an array containing all the rows that are in the Result object.