decision
奠 centers on formally settling or fixing something: making a decision, establishing a rule, or setting something in place. The given meaning 'decision' is the main application of this idea of definitive placement.
奠 is thought to combine 酋 (an offering vessel) with 大 (a stand or base), suggesting the act of placing an offering firmly on a stand, which extended to the idea of settling or establishing something definitively.
The top 酋 looks like a ceremonial vessel, and the bottom 大 is a sturdy stand. Picture placing the vessel firmly on the stand to mark a final decision.
For テン, imagine the number ten (テン) written on the stand as the final decision: ten -> テン, and the vessel is set down decisively.