Why EndDeviceEB left app less mem than CoorinatorEB?

 In SampleApp，the coordinator  can use osal_mem_alloc  to obtain about  2048B while the enddevice can use osal_mem_alloc to obtain about  1024B.
why the coordinator  obtained more mem than the enddevice? i am so confused.

i use the code to test:

      while(1)
      {
      char *p=NULL;
      p=osal_mem_alloc(512);
      if(p==NULL)
        SystemReset();
      else
        iLen+=512;
      } 



Then I have a look at the file SampleApp.map
 

CoorinatorEB-Pro:
133 561 bytes of CODE memory
26 bytes of DATA memory (+ 87 absolute )
6 895 bytes of XDATA memory
192 bytes of IDATA memory
8 bits of BIT memory
943 bytes of CONST memory
 

EndDeviceEB-Pro:
116 972 bytes of CODE memory
26 bytes of DATA memory (+ 87 absolute )
5 442 bytes of XDATA memory
192 bytes of IDATA memory
8 bits of BIT memory
879 bytes of CONST memory

that meas as follows,
with CoorinatorEB-Pro, the 6 895 bytes of XDATA memory have been used by system ,so left to the app will be 8192-6895=1297B
with EndDeviceEB-Pro, the 5442 bytes of XDATA memory have been used by system ,so left to the app will be 8192-5442=2750B

Why is not consistent with the above?