Energy itself has no unit, but Xin Yun has given energy a definition in his heart.
In Xin Yun's calculations, the energy of a dragon is measured in dragon power, and every dragon condensed within a Dragon Ball is regarded as one unit of energy, simply named as "one dragon"!
After condensing nine dragons, one reaches the gradeless Nine Stars; fusing the nine dragons into one achieves Ten Stars, and further understanding the power of the realm leads to the Bronze tier. Therefore, a Bronze One Star should possess the energy of nine dragons.
If one continues to cultivate, the Bronze tier takes nine as the unit; each time nine dragon powers are condensed, and these nine are unified into one, one star of energy is elevated. At the nine stars, the Dragon Ball contains nine "nine unified into one" dragon energies; fusing these nine dragons into one achieves Bronze Ten Stars, and understanding the abilities of dragons elevates to Silver One Star.