Assumed Temp Flex TO - Setting Window

Thank you for the advice Klaus. But this is what happens to me:

I choose flex takeoff (for ex. 45, 182 EPR) Before take off, I set Art to off, click the button on the throttles to activate the take off message. Then I push the throttles and let the engines spool up to 140 epr. Finally, I activate the auto throttle. I see the EPR spool up to 182. But when the CLAMP message displays, the engines spool down again to 140 and I have to push the throttles manually to 182. 

I don’t know what I am doing wrong. 

Jos