Deleting a point when measuring

[matt5CD1]

I am a Adobe Acrobat DC user.

When I am measuring a blue print I select multiple points of a area to get the square footage of a space. While selecting points, how do I delete a single previous selected point versus deleting all the points? 

[iacobra]

I am really struggling to get full use of the tool without knowing this, myself! 

I expected it to be very simple, Backspace or DEL or somtehing else intuitive. I must be missing something, right?