ok, how did you measure the points of the cut out shape when all you see is a rectangular representation of the object?
This little section is from the file that I made in Inkscape:
<path
id="path17222"
d="m -276.002,80.133 7.638,6.829 51.287,0 z"
style="fill:#cd0000;fill-opacity:1;stroke:#000000;stroke-width:2;stroke-linejoin:round;stroke-opacity:1"
inkscape:label="Face:1857"
inkscape:connector-curvature="0" />
I noticed the d="m -276.002,80.133 7.638,6.829 51.287,0 z" parts.
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grandstaircasedrawing.svg
(346427 bytes)
(Download count: 7755)
(The staircase svg just for the fun of it...)