Packets $($if any$)$ arrive at the beginning of the slot. Thus in the figure, packets $1,2$ and $3$ arrive in slot $0.$ If there are already packets in the queue, then the arriving packets join the end of the queue. Packets proceed towards the front of the queue in a FIFO manner. $2)$ After the arrivals have been added to the queue, if there are any queued packets, one or two of those packets $($depending on the number of available tokens$)$ will each remove a token from the token buffer and go to the output link during that slot. Thus, packets $1$ and $2$ each remove a token from the buffer $($since there are initially two tokens$)$ and go to the output link during slot $0.3)$ A new token is added to the token buffer if it is not full, since the token generation rate is r $=2$ token$/$slot$.4)$ Time then advances to the next time slot, and these steps repeat.