Agni Purana (Jyotisha Selections) · by Vyasa
Chapter 3 · Name Letters and Chakras
युद्धजयार्णवः (चक्राणि)
त्रयोदशी चतुर्दशी अष्टम्येका च सप्तमी ।प्रतिपत्त्रयोदश्यन्तास्तिथयो द्वादश स्मृताः ॥ २ ॥
In the full Agni Purana this is chapter 131, verse 2.
The 13th, the 14th, the 8th alone, and the 7th. The twelve tithis (moon days) are remembered as the first up to the 13th.
Simple meaning: These moon days are listed. Twelve moon days are counted from the first to the thirteenth.
चैत्रचक्रे तु संस्पर्शाज्जयलाभादिकं विदुः ।
In this wheel, odd places bring good results like victory and gain. Even places bring bad results.
युद्धकाले समुत्पन्ने यस्य नाम ह्युदाहृतम् ।
When war begins, look at the person's name and where it sits in the wheel. The sentence ends in the next verse.
जयस्तस्य सदाकालं सङ्ग्रामे चैव भीषणे ।
A good name sitting place brings victory. A short name means the warrior dies in battle.