Currently productivity targets can be setup against a month per user. Once the targets are set the users billable hours is measured against the target and then the graph shows the individuals progress towards the target.

There is no direct way to have productivity targets setup for each user against the projects that he works on, however there is a workaround this. You need to setup the Project and the tasks in the application as you normally would but then you would create sub-tasks with each of the users name and then input the target that they should reach in the Estimated hours field. The users time entry can then be tracked against the estimated hours setup in the respective project.