Matsya Purana — Solar–Lunar Motions
एतच्छतसहस्राणाम् एकत्रिंशत्तु वै स्मृतम् शतानि त्रीणि चान्यानि त्रयस्त्रिंशत्तथैव च //
etacchatasahasrāṇām ekatriṃśattu vai smṛtam śatāni trīṇi cānyāni trayastriṃśattathaiva ca //
Of these hundreds of thousands, tradition remembers the number as thirty-one; and in addition, three hundreds, and likewise thirty-three more.
This verse does not discuss Pralaya; it is a technical, tradition-based numerical statement about textual measure (counts such as groups of hundreds/thousands).
Directly, it does not prescribe dharma; indirectly, it supports dharmic study by indicating the Purāṇa’s traditional organization and remembered numerical measure used for recitation and transmission.
No Vāstu/temple rule is stated here; the significance is archival/ritual-recensional—helping track the Purāṇa’s extent for proper pāṭha (recitation) and manuscript cataloging.