The Meccan Revelations: Page 52 from Volume One

Its rank is ten spheres, which are the rest of the letters of the dictionary, and that is eighteen letters, each letter of which is composed of ten, just as each letter of those letters is related to nine spheres, and some to eight and seven, and nothing else, as we mentioned. So the number of spheres from which these letters were found, which are the simple ones that we mentioned, is two hundred. There are sixty-one spheres. As for the seventh level, the Z and L are lower than the Alif, and their nature is heat and dryness.