When you mark a job as In progress in your list of jobs, you see that a grey circle appears next to the status of the job.
You can click on this circle to indicate your progress in the job (e.g. if you already translated 20% of the job, or 50 or 75%, etc.)
The circle will be filled in with green depending on the progress you defined. The circle will be half full if you typed '50%', for example.
You can also change your progress in the job itself, by clicking on the circle in the Overview panel of the job.
