Available Memory on playground

I have tested two utlity for check free memory that are on arduino playground. These are availableMemory() and check_mem() and they are at http://www.arduino.cc/playground/Code/AvailableMemory. Running the same code I obtain:

ATMEGA 328 availableMemory() 40 check_mem() 231

ATMEGA 2560 availableMemory() 41 check_mem() 5918

How is it possible that values are so different? availableMemory() give the same value* on mega and uno but the first one has 4 times more memory!

of course on availableMemory() set **int size*, use 2048 with ATmega328, 1024 with ATmega 168, 8192 for mega 2560

Where does the "9920 for mega 2560" figure come from?

Where does the "9920 for mega 2560" figure come from?

of course I have done a mistake writing on the forum. The right value is 8192. I have correct it thanks!But the question is not solved. :~