Windows 7: Defragmenting on Windows 7

Hi everyone, I'm writing this message because I have currently one issue with the defragmentation on Windows 7. It is scheduled to run every wednesday at 1:00 AM as default but I have noticed that it is run more than once a week. For example, this week it occured on April 27th and this morning I found out it was run on April 28th too. The problem is that before the second running on April 28th, I saw on the scheduler that it was automatically to run on May 4th which is logical and makes sense. Is anyone else having this problem ? How can I fix it ?

Read through this Tutorial to see if you have set up your Defragmenter schedule correctly.

Disk Defragmenter Schedule- Turn On or Off