Data type for Custom Service NTF_CFG Write Indication

Dear support,

Currently I am implementing a Custom Service (CUSTS1 / CUSTS2) with a characteristic that as a Notify property (as in the Pillar examples), using SDK 5.0.3. I was wondering what the data type is for a _NTF_CFG handle; Is there a custom data type defined in the SDK or in one of the example projects?

By printing out the parameters->length field of the custs2_val_write_ind parameters in the handler for the CUSTS2_VAL_WRITE_IND message, I figured out that the number of bytes sent is 2. The value of parameters->value[0] toggles between 1 and 0 (when respectively enabling / disabling sending of notifications), the value of parameters[1] didn't change.

Can you point me to the specification somewhere? It's clear that byte0 is the ntf_cfg, does byte1 have any purpose?

Kind regards,
Arjan