Specifications of the motor of the kobuki

[joelle al hage]

Hello,
I need to know the torque motor specifications of the kobuki base, so I need the motor specification
I find the motor specifications in this link:
http://kobuki.yujinrobot.com/home-en/documentation/hardware/motor-details/

for the stall torque they get  33mN.m , but if I use the formula stall torque=(V*Kt)/R and I use the values that they give : V=12, Kt=10.913*10^-3, and R=1.5506 i get stall torque=84mN.m

have I make a fault in the calculation? because i can't figure out the cause of this difference?

Thank you