It is creating a classification based on the difference in minutes between deliver date and login date, from 1 (less than 30 minutes difference) to 4 (over 3h difference). If all those fields are already on the same table in your datamodel, you can basically include this line in the script as a new field and use this new field as the dimension.
If not, you will have to ApplyMap() or JOIN, or elaborate on how your model looks like so we can further assist.
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