there were some bugs around daylight savings that were fixed in the attendance plugin recently - can you confirm the version of the attendance plugin you have installed, delete the sessions it has created already, and see if you can reproduce it again? - Also the screenshot of settings at the top (14 -> 16th September) doesn't seem to match the sessions that were actually created so I suspect you may have managed to trigger the session creation twice - when creating sessions, it doesn't check "does a session at this time already exist", so if you open that add session page again and use similar sessions it will create "new" sessions based on whatever settings you have in the form.
Attendance (plugin)
Attendance (multiple sessions)
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