The simple idle income is already added to your counter because you need it there to pay your employees while offline.  

 

You can see that the welcome back window indicates how much did you earn while away. Please, notice the small text “already added” next to the idle amount.

 

Once you double or triple this “already added” amount, the game will tell you how much extra money will be added to your account (obviously, it will be the same amount when you press x2 or two times this amount when you press x3). This aggregate would be detailed in green.