You can see the color faintly under the white. Which tells me that the each square has a full square of the color tucked inside. Probably 1/4 of a fat quarter if that size is reasonable for a quilt square.
On a close look (ctrl+scroll button) it looks like the white is individual white triangles sewn together at the outer corners. Thus, creating a white square with a large X in the middle. Then the center points of the triangles (the right angles) are tacked to the middle, and a curve is folded in from that point to the seams joining the triangles into a square.
Aside from along the curved folded edges of the white triangles, there is no quilting.
Any way, that's what's happening with it, someone who actually knows about quilting could help you with proportions.