Can you refine the question? The 303 is an entry level phone and therefore it lacks the ability of having as many features and/or as much capability as some of the other models in the SPA family. The phone can only support up to 2 speed dials itself and this is dependent on the line key utilization. You can find some guidance in the attached –
You might consider using the speed dial (applications) functionality of the PBX instead as this would offer more offerings, albeit not in necessarily in a private manner as it would be in the phone itself.