First on your own Mac the number of projects is limited only by the amount of hard disk space you have. On the cloud the number of projects you can store their concurrently have depends on the package you purchased. With a Standard package you can have 6 projects in the cloud at a time. When you are done sharing a project for assessment you can remove it from the cloud freeing up the space for another project. There is a limit on the number of GB you can have stored in the cloud and download. See Pricing page for more information.