If you are using an instrument with a Roland BOSS GK pickup, you will find the necessary info in the GR-55 / SY-1000 / GP-10 Owner's Manuals regarding the suitable GK Settings for the specific device and GK divided pickup.
To find out the pickup parameters for third-party GK ready compatible instruments, such as Fishman guitars, Godin guitars, Brian Moore guitars, RMC pickups, Zeta guitars, Emerald guitars, Wilcox guitars/bass Lightwave Optical pickup, Graphtec Ghost pickup, and others like electric viola/violins, please contact the respective instrument manufacturers. They will provide the best GK Settings for your instrument's onboard GK pickup system.
For example of pickup options for the SY-1000 review the GK Setting Pickup Types below: