The fit uses ${\mathit m}_{{{\mathit B}^{+}}}$, (${\mathit m}_{{{\mathit B}^{0}}}{\mathit m}_{{{\mathit B}^{+}}}$), and ${\mathit m}_{{{\mathit B}^{0}}}$ to determine ${\mathit m}_{{{\mathit B}^{+}}}$, ${\mathit m}_{{{\mathit B}^{0}}}$, and the mass difference.