These are memory tweaks, so they should not directly affect CPU cycles, but tweaking these values too high can certainly affect the relative performance of the machine. On a performance-challenged machine your mileage will vary depending on how many other things you have running at the same time.
The 128MB of memory specified in the example becomes automatically reserved for OO provided that the Quickstart is selected. If Quickstart is not used, then the first time you open OO the 128MB gets carved out of memory regardless of whether the OO program needs it right then or not.
Therefore, on a machine without lots memory the values should be backed down starting at 128MB down to whatever helps the computer's quickness.