RX 480 8gb turn to 4gb after flash

Hi all

First of all credit and thanks to Heliox and Boysie

My GPU originally is RX 480 8GB reff card, after I flash Heliox ROM (RX480-30MhOTBLowEnergy) my GPU turn to 4GB. And I have huge GPU memory loss based on HWINFO

Below is my spec:-
claymore 7.4
Driver 16.10.3
RX 480 8GB reff (sapphire)


Below are my cpu spec




Can anyone advise me on this prob?

thank you