Sure, let’s treat potency as a linear function of the two concentrations. Define Cc = chamomile grams per unit volume, Cl = lavender grams per unit volume. Then potency P = α·Cc + β·Cl + γ. You’ll need a few measured potencies at known (Cc,Cl) pairs, set up the equations, and solve for α, β, and γ—ordinary least squares will give the best fit if the data are noisy. That’s the most efficient way to quantify the blend’s soothing effect.