Yes, once the Auto Spin has begun you can turn off the Auto 100 option, and at the next spin Picture Slots will recognise that you do not want to continue the Auto Spin feature.

Auto spin operates via a counter, so when you start you have 100 spins remaining and as each spin is completed the number of remaining spins is decreased by one.  Prior to each spin Picture Slots checks to see if the Auto 100 option is tuned on or off - if it is off then Auto Spin does nothing.