Fig 1. Sculpt Menu

Fig 1 shows you what you get when you use the <4> or <5> keys:

<4> - Push

Press and hold the <4> key to push in the surface at the mouse pointer location.

<5> - Pull

Press and hold the <5> key to pull out the surface at the mouse pointer location.

<G> - Sculpt Marked

<Shift-G> - Sculpt Marked Inwards