A coordinate crop is useful when the part you need is not in the centre. It gives you an exact rectangle instead of an automatic aspect crop that chooses the largest possible area.
In Coordinate Image Cropper, x measures the left offset and y measures the top offset. Width and height describe the rectangle to keep. Coordinates refer to source pixels after supported camera orientation correction.
A rectangle you can calculate
For a 400 by 300 source, x 100, y 50, width 200 and height 100 keep a 200 by 100 region. Its right edge reaches source position 300 and its lower edge reaches 150.
The crop must remain inside the source. An x value of 350 with a width of 100 would extend beyond a 400 pixel image and is rejected rather than silently clipped.
The browser overlay shows the selected region on a scaled preview. Its apparent size on screen is not a new coordinate system; a displayed 200 pixel wide preview can still represent a much larger source.
Cropping does not resize the kept pixels
The output dimensions are the width and height of the selected rectangle. If you need that region enlarged or reduced afterwards, use the resizer as a separate step.
Batch cropping uses the same coordinates for each image. That only makes sense when the sources have compatible dimensions and framing. One smaller image can make the shared rectangle invalid.
Keep the original file before experimenting. Moving the crop is easier from the untouched source than from a previous crop that has already removed surrounding content.
Review the preview for cut edges and the reported dimensions for the exact rectangle. Those two checks answer different questions: whether the right region was selected and whether its size is the one you intended.