In the previous post entitled "Nineteen - The Authenticity Detector of the Qur'an", when discuss about the seventh checksum, it is stated that :
There are 29 surah in the Qur'an which have initials or fawatih in the first verse, such as: alif, lam, mim, ra, shad, nun. Out of those 29 surah, the 15th surah in this list is the surah Al-Ankabut which is the 29th surah of the Qur'an. This surah divide the list of initials-have surah into 2 parts, 14 chapters before this surah and 14 surah after this surah.