How many contacts can be stored on my Gigaset handsets?
You can check remaining number of entries of your Gigaset handset. Open Directory, check Options / Available Memory.
Most handsets provides an entry in the context menu of the directory which shows the - approximately - amount of free contacts in the directory. Approximately, because it strongly depends on the content of each mobile contact (see question above) how many contacts will be created on the Gigaset handset side.