All of those schedules are created by default in Tableau Online so you cannot create or delete them.
Do you mean you have a data source/workbook being refreshed too many time?
If you want to delete a scheduled refresh for a specific data source here is one way to do it:
In the schedules tab you are in in the screenshot look at the tasks field. If there is a number > 0 it means that there is an data source using this schedule. Select the Schedule and you will get a list of workbooks/data sources using this schedule. Select the "..." beside the data source/workbook and select "Delete". This will remove the data source from this refresh schedule.