Ex9 11

$\def\abs#1{|#1|}\def\i{\mathbf {i}}\def\ket#1{|{#1}\rangle}\def\bra#1{\langle{#1}|}\def\braket#1#2{\langle{#1}|{#2}\rangle}\def\tr{\mathord{\mbox{tr}}}\mathbf{Exercise\ 9.11}$

Why doesn't applying amplitude amplification to the output of a first application of amplitude amplification not result in an additional square root reduction in the query complexity?