Lesson writers can currently only check out one lesson to work on at a time. CMS may suggest otherwise, however we have restricted this for some asset types ensure that lessons don't sit unwritten in lesson writer queues for long periods of time. This means lessons are available on a first-come first-serve basis. This helps us get new content live on the site for our students as quickly as possible.
Other projects may allow two or three titles at a time, usually because those projects take less time to complete. When you're in the checkout pool, continue to check out titles until you're prompted to enter your work queue.