Section placement file

I need to add a section to my section placement file at the specific place in RAM. I tried this to place a section at 10 bytes offset from the end of RAM:

    <ProgramSection alignment="4" load="No" name=".bootloader_data" start="$(RAM_START:$(SRAM_START:)) + $(SRAMSIZE) - 10"  address_symbol="__bootloader_data_start" />

but I get syntax error.

To be honest, I have no clue what $(RAM_START:$(SRAM_START:)) syntax means and whether I can use $(SRAMSIZE) variable in section placement file. Can you please provide some documentation of this?