The transmissiion will not shift to a higher gear than you have selected. It will, however, downshift based on throttle postion, load etc.
Think of it this way.
If you select gear 4, you are essentially driving with a 4 speed trasnsmission.
You can start in 1 and have total control of up shifting with the paddles. The car will not shift any higher than what you tell it to.
When slowing down, or punching the throttle, etc, the transmission will downshift as it thinks is necessary.
In "S" mode you may also upshift and downshift by pushing the gear selector lever forward for up and back for down. You may use either the paddles or the gear lever whenever in "S" mode.