Muhammad said: "In layers" is an adjective describing "seven"; meaning: He created seven [heavens] that are layered.
قَالَ محمدٌ: (طباقًا) من نعت (سبع)؛ أَيْ: خَلَقَ سَبْعًا ذَاتَ أَطْبَاقٍ.
