If you have auto tuner going you probably do not need to adjust it. That
recommendation is from the manual "Recovering your system". It's a
section intended for someone who is restoring to a new hardware box, in
dedicated state, with no performance tuner running. As a recommended
initial size. It's also followed by this statement:
"For a more precise setting of the QMCHPOOL system value, see the Types of
memory pools information center topic."