Part sticking out no matter what, Blender

[Player_SPS]

I’m new to blender, and I’m trying to create a pillar from this course: Use Blender to Create Beautiful 3D models for Video Games, 3D Printing & More. Beginners Level Course, on Udemy. But every time I try extruding and scaling down on the x-axis, there’s this part left out, and I don’t even know where it came from. Here are a few images describing what’s happening:

Before

Selection

Selected

Then I extruded and scaled it down, and this kept happening:

Extruded and Scaled Down + Problem

Problem

Problem

These are the things I tried:

• Deleting the extra thingy (The vertices would stay)
• Restarting the pillar (the problem stayed)
• Restarting blender (the problem stayed)

Extra Info

It was made from a cube

[NP5]

Tick ‘Clipping’ in the mirror modifier panel.

Good images, just generally full screenshots have all the panel info.

General Q&A note
Help us all to help you.
Please give FULL screenshots with any questions. With the relevant panels open.
Also, include the lecture time and name/number that is relevant to the problem/issue.
The screenshot can be done by Blender itself, via the ‘Window’ menu bar top left hand side.
On that menu drop down is ‘save screenshot’.
Close ups additionally where they help.

[Player_SPS]

Thanks, it worked, and I’ll do those next time I have a question.