Thank you for pointing this out to us. I have alerted the appropriate people, and the change will be made to the Getting Started Guide. The correct answer is, "There is no need to change Apache Performance Cache setting on Leopard Server. Use the default setting."
I was informed that all of our web tests were done with the default setting. Therefore, there is no need to change the performance cache setting on Leopard Server. The default should be fine.
Please let me know if you still run into difficulty.