used memory confusion

[genap]

I am using XS1-U8A in my project.
When I compile the project, the console shows:

Memory available: 65536, used: 54064

But when I create an upgrade binary, the file size is 40192.
Do I miss something ?

[segher]

Uninitialised / zero-initialised data ("bss") is
not stored in the program image. You probably
have a few big buffers.

[genap]

thanks a lot.
forgot about sharing data / code space..