Typo in poisson_neuron.ipynb?

As for the Poisson approximation of the binomial, I think the rate parameter should always be 'rT'(M*r*dt = T/dt*r*dt = rT), however, your formula gives '-rdt' as a rate parameter in the Poisson pdf, I have programmed and ran a simulation, it turns out your formula gives a '>1 probability value'. 