Natyashastra
निष्क्रामसन्निपातान्ते नित्यमष्टकलो भवेत् । एष युग्मे कलापातविकल्पोऽङ्गुलिभिः कृतः ॥ ४३॥
At the end of the Niṣkrāma and Sannipāta, there should always be eight Kalās. This is the method of indicating the variation in the dropping of Kalās in a Yuga, performed through fingers.
english translation
niSkrAmasannipAtAnte nityamaSTakalo bhavet । eSa yugme kalApAtavikalpo'GgulibhiH kRtaH ॥ 43॥
hk transliteration by Sanscript