आदावन्ते गुरूणी मध्ये च लघूनि बालतः प्रभृति । अष्टौ द्वादश षोडश विंशतिरपि वाक्षराणि स्युः ॥ ९९॥
At the beginning, the syllables are long, in the middle short, and for the bāla (short) Āsārita, accordingly. There are eight, twelve, sixteen, and even twenty syllables in the respective Upavahanas.
english translation