Brihat Parashara Hora Shastra
यत्संख्ये वर्णदो लग्नात् तत्तत्संख्याक्रमेण तु। क्रमयुत्क्रमभेदेन दशा स्यादोजयुग्मयो॥ १५॥
If the natal Lagn is an odd Rāśi, the counting of Dashas is clockwise, otherwise anticlockwise. Lagn Dasha years will equal the number of Rāśis, intervening between the natal Lagn and Varnad. Similarly for other Bhavas.
english translation
yatsaMkhye varNado lagnAt tattatsaMkhyAkrameNa tu। kramayutkramabhedena dazA syAdojayugmayo॥ 15॥
hk transliteration by Sanscript