I'm watching a tutorial, and the instructor is using extrude method to get a notch in a sphere using the extrude method. He's going to fast to understand how he achieves this. Its the 02:58, where he says he's going to extrude that little bit.
https://www.youtube.com/watch?v=FV66bVT1Tog&t=180s
This is what I select on my sphere, and the result I get when extruding.