How does kobuki iclebo (turtleBot) motor work with robotics toolbox?

When using ROS in a direct way, I send a Twist msg with velocity (linear and angular) parameters that are adding on to the previous msgs to accumulate to a sum of 6 "Velocities".

But when using MATLAB's equivalent, it is quite different - I send a msg and instead of a constant velocity, I get some acceleration and then it stops after a while.

In other words - I would like to know what does send(motor, TwistMSG) does exactly Also - are there more parameters that could help me control the movement in a better way? (acceleration, duration, specific amount of rounds for each motor, etc..)