The temporary income doubler is designed to make higher profits during your online management of this specific TV station. It will also double your offline income if you close the game after watching ads (if you leave the app with 1 hour of ad doubler running, this bonus will be applied to your offline earnings the next time you log in). 
 
However, you can lose this multiplier if you visit another level right after its activation. We would recommend traveling between TV stations before you activate the temporary income doubler. In any case, the team is optimizing this feature for further updates.