Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
सौम्यस्यार्द्धेन पापस्य समग्रेणेति निश्चयः ।गुणकघ्नाश्चायुरंशाः संस्कारोऽयमुदाहृतः ॥ १३२ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 132.
It is settled that the cut is half for a good planet and whole for a bad planet. The lifespan parts are multiplied by the multiplier. This is the correction as given.
Simple meaning: A good planet is cut by half and a bad planet by the whole amount.
आयुरंशकलाभक्ताद्विंशत्याब्दा इनाहतम् ।
The lifespan in minutes is divided to give years, months and days.
लग्नायुरंशास्त्रिगुणा दिग्भक्ता स्युः समास्ततः ।
The rising sign's parts are turned into years and months.
सबलेंगेभतुल्याब्दैर्युतमायुर्भवेत्स्फुटम् ।
A strong rising sign adds years equal to its signs, and months from its degrees.