The first time you start iStudiez Pro, the app offers you to load Sample Data.
Sample Data is a set of courses, classes, instructors, etc. for you to get familiar with the app and the way the data is organized there.
You are welcome to interact with Sample Data any way you want.
Do the following to delete Sample Data from iStudiez Pro:
Go to iStudiez Pro > Settings (on Windows) > Data Managing > Delete App Data
NOTE, it will delete ALL data you have in the app.