The multiload applet calculates the memory like this:

    user = mem.used - mem.buffer - mem.shared;
        
    user    = rint (Maximum * (float)user   / mem.total);
    shared  = rint (Maximum * (float)mem.shared / mem.total);
    buffer  = rint (Maximum * (float)mem.buffer / mem.total);
    free    = rint (Maximum * (float)mem.free / mem.total);

mem.cached, which is a very significant portion of my memory here, that was
lands in user, which always leads to the false assumption, my memory was
80% - 90% used, where it's really 40% (the -/+ buffers/cache line in free
output). I suggest the following computation:

    user = mem.used - mem.buffer - mem.shared - mem.cached;
        
    user    = rint (Maximum * (float)user   / mem.total);
    shared  = rint (Maximum * (float)mem.shared / mem.total);
    buffer  = rint (Maximum * (float)(mem.buffer + mem.cached) / mem.total);
    free    = rint (Maximum * (float)mem.free / mem.total);

Attached is a patch.