extremely high throughput

I run iperf with option "-u -b 10M"(ex1) and "-u -b 50M"(ex2), but at some point the bitrate output looks strange.
ex1) 15:20:34 --> 634Mbps >> 10M !!
(part of the output as below)
Tue Jul 1 15:20:07 2025 [ 5] 1926.00-1927.00 sec 1.22 MBytes 10.3 Mbits/sec 0.800 ms 0/886 (0%)
Tue Jul 1 15:20:08 2025 [ 5] 1927.00-1928.00 sec 1.19 MBytes 10.0 Mbits/sec 0.584 ms 0/865 (0%)
Tue Jul 1 15:20:09 2025 [ 5] 1928.00-1929.00 sec 1.17 MBytes 9.80 Mbits/sec 0.439 ms 0/846 (0%)
Tue Jul 1 15:20:10 2025 [ 5] 1929.00-1930.00 sec 1.21 MBytes 10.1 Mbits/sec 1.291 ms 0/875 (0%)
Tue Jul 1 15:20:11 2025 [ 5] 1930.00-1931.00 sec 973 KBytes 7.97 Mbits/sec 1.055 ms 35/723 (4.8%)
Tue Jul 1 15:20:12 2025 [ 5] 1931.00-1932.06 sec 467 KBytes 3.60 Mbits/sec 1.229 ms 0/330 (0%)
Tue Jul 1 15:20:13 2025 [ 5] 1932.06-1933.14 sec 472 KBytes 3.60 Mbits/sec 0.792 ms 279/613 (46%)
Tue Jul 1 15:20:14 2025 [ 5] 1933.14-1934.08 sec 560 KBytes 4.84 Mbits/sec 1.202 ms 445/841 (53%)
Tue Jul 1 15:20:34 2025 [ 5] 1934.08-1954.09 sec 781 KBytes 320 Kbits/sec 1.320 ms 353/905 (39%)
Tue Jul 1 15:20:34 2025 [ 5] 1954.09-1954.10 sec 139 KBytes **683 Mbits/sec** 3.503 ms 0/98 (0%)
Tue Jul 1 15:20:35 2025 [ 5] 1954.10-1955.00 sec 0.00 Bytes 0.00 bits/sec 3.503 ms 0/0 (0%)
Tue Jul 1 15:20:36 2025 [ 5] 1955.00-1956.00 sec 0.00 Bytes 0.00 bits/sec 3.503 ms 0/0 (0%)
Tue Jul 1 15:20:37 2025 [ 5] 1956.00-1957.00 sec 0.00 Bytes 0.00 bits/sec 3.503 ms 0/0 (0%)
Tue Jul 1 15:20:38 2025 [ 5] 1957.00-1958.00 sec 0.00 Bytes 0.00 bits/sec 3.503 ms 0/0 (0%)
Tue Jul 1 15:20:39 2025 [ 5] 1958.00-1959.00 sec 0.00 Bytes 0.00 bits/sec 3.503 ms 0/0 (0%)

ex2) 08:21:17 --> 112Mbps >> 50M !!
(part of the output as below)
Thu Jul 17 08:21:13 2025 [ 5] 63473.00-63474.00 sec 1.79 MBytes 15.0 Mbits/sec 0.562 ms 3022/4320 (70%)
Thu Jul 17 08:21:14 2025 [ 5] 63474.00-63475.00 sec 1.69 MBytes 14.2 Mbits/sec 0.383 ms 3098/4320 (72%)
Thu Jul 17 08:21:15 2025 [ 5] 63475.00-63476.00 sec 897 KBytes 7.34 Mbits/sec 0.219 ms 1853/2487 (75%)
Thu Jul 17 08:21:16 2025 [ 5] 63476.00-63477.00 sec 998 KBytes 8.18 Mbits/sec 0.259 ms 36/742 (4.9%)
Thu Jul 17 08:21:17 2025 [ 5] 63477.00-63478.00 sec 13.4 MBytes **112 Mbits/sec** 0.385 ms 541/10240 (5.3%)
Thu Jul 17 08:21:18 2025 [ 5] 63478.00-63479.00 sec 5.86 MBytes 49.2 Mbits/sec 0.299 ms 206/4451 (4.6%)
Thu Jul 17 08:21:19 2025 [ 5] 63479.00-63480.00 sec 5.69 MBytes 47.7 Mbits/sec 0.329 ms 199/4317 (4.6%)
Thu Jul 17 08:21:20 2025 [ 5] 63480.00-63481.00 sec 5.68 MBytes 47.6 Mbits/sec 0.278 ms 199/4313 (4.6%)
Thu Jul 17 08:21:21 2025 [ 5] 63481.00-63482.00 sec 5.69 MBytes 47.7 Mbits/sec 0.294 ms 199/4316 (4.6%)
Thu Jul 17 08:21:22 2025 [ 5] 63482.00-63483.00 sec 5.68 MBytes 47.7 Mbits/sec 0.290 ms 199/4315 (4.6%)

Anyone could tell me how this happened ?