First, consider the pink flow: at time 1, the flit 'U' is sent to the first buffer; at time 2, the flit 'U' goes through the next buffer (assuming the computation of the route takes no time), and the flit 'V' is sent to the first buffer, and so on.
first consider the pink flow at time 1 the flit 'u' is sent to the first buffer; at time 2 the flit 'u' goes through the next buffer (assuming the computation of the route takes no time) and the flit 'v' is sent to the first buffer and so on