How to determine the App RAM base address in the linker script?

I understand part of ram is used by the softdevice, but I see different addresses are used in different examples that use the same softdevice, namely S132. For example,

in ble_app_hrs/pca10040/s132/armgcc/ble_app_hrs_gcc_nrf52.ld, RAM (rwx) : ORIGIN = 0x20002c38, LENGTH = 0xd3c8

In ble_app_uart/pca10040/s132/armgcc/ble_app_uart_gcc_nrf52.ld, RAM (rwx) : ORIGIN = 0x20002128, LENGTH = 0xded8

How is the exactly value being determined?