Please look the L102
https://github.com/stm32duino/STM32FreeRTOS/blob/master/src/FreeRTOSConfig_Default.h

here is my result I think it should change to
#define configTOTAL_HEAP_SIZE ((size_t)(&_estack - (uint32_t)&_Min_Stack_Size - &_end))

I use printf to print the value of _Min_Stack_Size it always wrong, but I add the & as &_Min_Stack_Size , it will be the right value that I set in the ld file.

SO I the heap size shoud minus the _Min_Stack_Size set to 0x400?