How long is your Z axis?
Try a pen and see it it’s better.
That is fast and deep. Both your cuts are small meaning your tool didn’t catch up to the pressure you put on it dragging it through the material so hard. I’m sure a pen will show much closer dimensions. Slow down or cut it in 2 passes and your dimensions will be better. You can have fast or precise not both at the same time. Also shorten your z axis by moving the material up and I bet the dimensions will be closer as well.
How big is your overall machine?
A picture would eliminate some of the guesses I just made. And I could narrow it down a bit but those are the things everyone seems to be doing wrong at the beginning.