I measured the round trip losses with new beam spot which has more stable IR transmission. The round trip losses are 139 ppm.

P_res = 245; % BAB reflection power on resonance (uW)

P_in = 362;   % BAB reflection power off resonance (uW)

R_gamma = P_res/P_in;

gamma = 0.05; % uncoupled power to the cavity: 5% from mode mismatch

R = (R_gamma-gamma)/(1-gamma);

T = 0.00136; % input mirror transmissivity

L = (T/2)*(1-R)/(1+R) = 139 ppm