It does not allow you to flash custom, unsigned software like TWRP itself or custom ROMs. The notation simply denotes its version. This limited interface is why installing a custom recovery like TWRP is necessary for advanced modifications.
How to Install TWRP Recovery from Android System Recovery android system recovery 3e install twrp
Boot into Download Mode. For older devices, hold Volume Down + Home + Power . For newer devices, hold Volume Down + Bixby/Power while plugging in the USB cable. It does not allow you to flash custom,