Brihat Parashara Hora Shastra
क्रमात् सूर्यादिखेटेषु स्वस्वोच्चस्थानगेष्विह । नन्देन्दवस्तच्वमितास्तिथयोऽर्काः शरेन्दवः ॥ ६॥
19, 25, 15, 12, 15, 21 and 20 are the number of years, contributed by the Grahas, from Sūrya etc., when in exaltation. These are half of the above in debilitation.
english translation
kramAt sUryAdikheTeSu svasvoccasthAnageSviha । nandendavastacvamitAstithayo'rkAH zarendavaH ॥ 6॥
hk transliteration by Sanscript