X-Headstage is manufactured based on advanced packaging technology such that there are multiple ICs inside each chip. X3SR32 has two Intan RHS2116 dies inside therefore each die is connected to one of the two X3BtB connectors (to maintain the compatibility with other X3 series chips).
Therefore, only 16 out of 32ch (18 if GND and Ref are included) are activated. See the pinout mapping section for more information.