Suppose a 100 Gbit/sec link connects Seattle and Toronto. If Seattle is sending hefty 2 kbit packets, it can send at a rate of (100 Gbit/sec)/2 kbit/pkt) = 5×107 pkts/sec.
The straight-line (great circle) distance between Seattle and Toronto is 2,073 miles. The speed of light through fiber is about 123,000 miles/sec. It takes the first packet to encounter congestion at Toronto (2,073 miles)/(123,000 miles/sec) = 0.017 sec to travel from Seattle to Toronto. In that time Seattle will have sent another (5×107 pkts/sec)×(0.017 sec) = 850,000 packets.