In your Motivity session notes, there is a new option to automatically calculate and display billing units for a session based on minutes per unit and the session duration.
To set this up, you will navigate to "Settings" --> "Note Templates" and then select the note template for which you would like to add a billing units field. 
To add the field, click "+" --> "Imported Fields" --> "Note Fields" --> "Note Duration"
From there, you can select if you want that field to display the note duration as time (i.e. 2 hours), billing units (i.e. 8) or both. If you select units or time and units, Motivity will ask you to input how many minutes equate to one unit (Minutes per unit) as well as how you would like Motivity to round (up on partial units, down on partial units, or based on the halfway point).
Note: Here, you can also title your field:
Once you have made your selections, make sure to "Update" your template.
Now when utilizing this note template, the billing units will automatically calculate.
The example below shows a 1-hour session note automatically displaying 4 units based on 15 minutes per unit entered into the template: