Depending on the model, you can expand the index count. For information on compatible models, see the following.
1.5 Supported Features
To use the [Extended] setting for GP3000 series, attach a GP3000 Function Expansion Memory (option). On the [System Settings] window, select [Display Unit]. In the [Extended Settings] tab, set [Function Expansion Memory] to [8M].
While the display unit is running, do not remove the GP3000 Function Expansion Memory (option).