There are two ways of managing non-billable time in Streamtime:
Create a non-billable/admin job > label it "non-billable" and treat it as a regular job. The fact that you're labeling this job "non-billable" gives you an opportunity to exclude these jobs from your profitability reports by using filters.
2. Add a non-billable item into a billable job.
You can then report on non-billable items by heading to jobs > time > group by: item name > filters: item name consist "NB"(for example)