Can someone explain why the first line is always the same?

ac:/# top q b n 2 | grep "CPU st"
CPU states:   6.1% user,   1.7% system,   0.1% nice,  92.1% idle
CPU states:  53.3% user,  46.7% system,   0.0% nice,   0.0% idle
ac:/# top q b n 2 | grep "CPU st"
CPU states:   6.1% user,   1.7% system,   0.1% nice,  92.1% idle
CPU states:  33.3% user,  66.7% system,   0.0% nice,   0.0% idle
ac:/# top q b n 2 | grep "CPU st"
CPU states:   6.1% user,   1.7% system,   0.1% nice,  92.1% idle
CPU states:  53.8% user,  46.2% system,   0.0% nice,   0.0% idle
ac:/# top q b n 2 | grep "CPU st"
CPU states:   6.1% user,   1.7% system,   0.1% nice,  92.1% idle
CPU states:  50.0% user,  50.0% system,   0.0% nice,   0.0% idle
ac:/# top q b n 2 | grep "CPU st"
CPU states:   6.1% user,   1.7% system,   0.1% nice,  92.1% idle
CPU states:  75.0% user,  25.0% system,   0.0% nice,   0.0% idle
ac:/# 

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