The discrepancy between Largest Unused Block and
the Total Unused Memory is an issue known as
fragmentation. This is like breaking up ice using an
ice pick. In such a case you do not have any less ice, you
simply have smaller blocks. RAM Charger's "total memory" is
the only place you can see the sum total of all the broken
pieces of memory.
On a Mac, memory is fragmented as you operate. By
watching as you work, perhaps check marking both Total and
Largest in the RAM Charger Pull-down menu, you should be
able to determine what action(s) are fragmenting your
memory. Example: Start three applications, and quit the
second one started; this leaves a "hole" in memory between
the other two, and your memory is fragmented. Then, examine
More About This Mac in "view:by location in Memory".
By watching your Total and Largest blocks, and using More
About This Mac in "view:by location in Memory" you may be
able to slightly modify your usage to avoid serious
fragmentation (without disrupting your life). At the very
least, you should be able to understand it and minimize its
influence upon you.
The only reason you care about fragmentation is that
applications require an initial "starting size" chunk of
memory to open. Even with RAM Charger enabled, applications
will require a "starting size", which is shown in the Get
Info window for the application.
The good point is that RAM Charger allows you to reduce
the starting size required for applications, since they are
able to access the "other chunks" of memory for operation
needs. On the other hand, without RAM Charger applications
are limited to their starting size; this is why the "total
memory" is not shown without RAM Charger - without RAM
Charger it is superfluous information.
With RAM Charger applications start smaller, causing less
of a "big" hole fragmentation when they are quit, and
applications can access fragmented memory. Both of these are
reasons why RAM Charger helps with fragmentation issues,
though it does not solve the problems completely.
So, you may be able to reduce the starting size for each
applicaiton to a size that allows it to start when you do
not have a large block. Unfortunately, some applications
will refuse to start if you set the starting size too low,
so you will have to experiment. The lowest size may vary
somewhat based on your your application's configuration
(especially plugins and extensions).