velocity and delta_theta

[LongfeiProjects]

V-REP-YouBot-Demo/7_Demo_youBotPickAndPlace/code/NextState.py

Line 19 in 6faa738

theta_dot = delta_theta

I went across the tutorial, and came across with this confusion:
I suppose theta_dot is the derivative of theta with respect to time, namely wheel rotating(angular) velocity. If that stands, theta_dot is equal to speed[0,5:], instead of delta_theta, which is a step rotation(\omega * \delta t)