089 

This is probably the gauge of the string, measured in inches (".089" means "0.089 inches"). The gauge of an electric bass string refers to its diameter, and thicker gauge strings tend to produce a more powerful sound, while thinner gauge strings produce a clearer sound.

However, it is important to note that the choice of bass string gauge also depends on many other factors, such as the type of music you play, your playing style and your personal preferences. It is therefore advisable to try out different string sizes to find the one that best suits your needs.