Navkar mantra ke akshar (letters) ki kul sankhya 68 mani jaati hai. Anusvar ki alag se ginti Jain scriptures me pramukh roop se 68 akshar ki ginti ke antaragat hi hoti hai; alag se “anusvar ki sankhya” ki standard ganaati aam taur par nahi di jaati. Nasal (anusvar-sangat) swar ya letter transliteration ke hisaab se alag-alag prakar se dikh sakte hain, lekin mool mantrat ki rasmi sankhya 68 akshar hi mani jaati hai.

You can read more here and here