Does anyone know what the data means in the
memory prefs

Which memory prefs ?
The file in the Prefs folder, the numbers in
the GetInfo Window, or in the SIZE resource
or somewhere else ?

Any of them would be great, but mainly the
"Memory Preferences" in the Prefrences
folde

The "Memory Preferences" file in OS 8.6
contains only a 4 byte "DATA" resource.
It turns out that it's the X,Y coordinates of
the Control Panels window.
The values are saved between sessions, so
that it always opens up in the same place as
it was last found.
Perhaps more interesting from a memory
hacking point of view are the "Mac OS
Preferences" and "System Preferences" files.
Both of these are changed whenever you make
modifications in the Memory Control Panel
(Isn't list by mod date wonderful !). The
resouces in "Mac OS References" are a bit big
to see what is changed easily -Get a copy of
ResCompare to find out exactly what changes
where here.
The "vm " resource of the "System
Preferences" file is used to set up virtual
memory
the 1st 4 bytes are an off/on flag for vm
(0000 0001 being ON)
next comes the amount of virtual mem to be
allocated (in hexadecimal)
and finally the name of the drive to use for
VM (as a length preceded pascal string).
The dccf and mloc resources should also fall
easily to an analysis of the changes made by
using the Memory Control Panel.
If you are serious about messing with these,
be sure to have a backup method of starting
up your Mac before going too crazy with them.
-enjoy !

Thank-you. I probably wouldn't have founf this out!