Ask for help: bookmarks generated automatically


I am using a MarginNote 3 app on my iPad Pro. Today, I was reading a textbook, and create a bookmark for marking the current reading position. All of sudden, the app creates a bookmark for every page in this document. I don’t know if I touch any wrong spot to cause this. Could anyone help me to delete all these useless bookmarks in a easy way, instead of moving onto each page and tapping the remove button?