I think I've found a bug in FreeRTOS heap usage viewer.
I'm using memory scheme 5 for heap (two separate memory regions).
When I get informations about heap usage I see the following image:
The first two rows (the total memory and the first region) display the correct informations, while the third displays wrong heap usage: I verified the usage with free blocks linked list (xStart variable in heap_5.c suorce file). The heap base and heap end informations are correct, heap usage, free space and heap usage graph informations are not.