The Auto 100 feature has been designed to allow the flow of the game to continue while you are off somewhere else.  When you turn on the "Auto 100" option Picture Slots, after pressing the "Spin" button begins an auto play of 100 turns that requires no user intervention.

Wins are calculated along the way, free games are played without you needing to sit there and watch it.

You can not gamble your winnings while the 'Auto 100' is running.