VSB stands for Visual Scheduler Builder. It's where you go to build your schedules in RecStaff. The Calendar Canvas is the back drop of the Visual Scheduler Builder (VSB). The Calendar Canvas gets rendered each time you create a new schedule. It's rendered based on the time blocks that have been defined for your schedule type.
You'll note the end times of the time blocks highlighted in yellow below are reflected on the calendar canvas above as greyed out meaning no shifts should be added. Time blocks are also used to create the availability form staff fill out to let you know when they can or cannot work. All shifts should fall within the time blocks you created.