Available Spaces/Max Students refer to how many Students are able to be present in one specific Lesson. If you wish to define this, navigate to Activity > Jobs > select the Job > Actions > Edit and adjust the ‘Max Students’ number field found under the ‘More Settings’ tab. The number input here will be the default total number of Students which can appear on any given Lesson for this Job.
You can additionally edit the number of Students on a Lesson by Lesson basis. If you have set up the 'Max Students' on the Job, then when editing an individual Lesson via Activity > Calendar > select the Lesson > Actions > Edit, you can configure the 'Max Students' for that Lesson alone.
Editing a Job’s Max Students.