A higher bulk modulus indicates a less compressible medium. For example, steel has a bulk modulus of 160 x 109 Pa while air has a bulk modulus of about 105 Pa.
The bulk modulus is always positive. Increasing the pressure (Dp > 0) causes a decrease in the volume (DV < 0) and decreasing the pressure (Dp < 0) causes an increase in the volume (DV > 0).