not supported for flashing

hello and have a nice day.

--------- 2019-04-30 16:42:31 ---------
SigmaKey 2.30.04 HiSi: Write firmware
(ADB) Writing flash...UPDATE.APP
Firmware: Rhone_Global_EMUI8.0
This operation may brick the phone! Are you sure you want to proceed? [YES]
Phone model: RNE-L21
Version: :RNE-L21 8.0.0.344(C185)
Preparing...This Android security patch level is not supported.
Please wait for future updates.