The wheel collapses Purnima and Amavasya into spoke #15. Pratipada sits at the top (12 o'clock) and the cycle runs clockwise.
What you are looking at
The base scoring pairs the Shukla and Krishna paksha presiding deities of Narada Purana 56.133b–135, folds them onto the Shiva / Shakti / Vishnu axes, and adds Jayanti reinforcements (Maha Shivratri, Krishna Janmashtami, Ram Navami, the ten avatars, the major Devi vrats, and the systemic monthly recurrences of Ekadashi, Pradosh, and Masik Shivratri). The full methodology, folding table, and source citations live in the accompanying essay.
Three patterns are visible at a glance: Vishnu owns the digestive middle (Chaturthi, Ekadashi, Dwadashi). Shiva owns the closing tithis (Ashtami, Chaturdashi, Purnima/Amavasya). Shakti claims the generative tithis (Panchami, Shashthi, Trayodashi).