If you are using
https://oneblockwonder.com/design-helper/, double check that you have entered the correct size for the width of image. It defaults to 40" width, so if your image is showing only 20" of fabric, it will show you a very different size (and count) of triangles/hexagons than if you enter the correct width.
Additionally, I believe that this tool does *not* account for seam allowances; it shows you hexagons as they would appear if you put them together with raw edge applique (or something else similar) rather than sewing them together with a 1/4" seams.