Work logs can be categorized or extra information can be added to them thanks to attributes. They can represent an invoice id, type of work performed like testing, development etc, or you can differentiate billable time from non billable time or overtimes. It completely depends on you needs. In order for a work log attribute to be visible on the "Log Work Dialog", it needs to be defined on administration of the add-on.
If any work log attributes are defined in the administration section they will appear just after the description part of the worklog dialog as shown on the screenshot. Depending on the configuration some of them may be mandatory for worklogs and they are marked with usual *next to their label name. For example in the screenshot "Work Type" work log attribute is mandatory and you will not be able to log work without specifying a value for it.
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