no option to change bitrate

current install of Media encoder, tryingto transcodw soem H'254 drone footage to an edit friendly form....tried various DNx options but I'm always ending up with files as big as the originals ( nearly!) ...every single tutorial I see shows an option to change the bit reate of the output ..that option just isn't in my drop down menu in video settings???

EDIT --- just found out DNxHR cannot be adjusted by bit rate!