Houston, I don't understand the selection tool

[AhabGreybeard]

@PixLab

Please forgive me, I come from GIMP,

So do I

@PixLab

so I still have a lot to learn about Krita,

So do most of us

Please see this topic:
Anti-aliasing + Fuziness in Contiguous Selection tool is causing huge area to be selected as semi-transparent pixels

Summary: turn anti-aliasing off in the Tool Options docker.