7i33TA and electrocraft max 400 driver connection.

Hello, I need to connect the 7i33TA card to the electrocraft max-400 servo driver but I have a question. The manual of the 7i33TA card says that I must connect DRV to drive INPUT and 7I33 GND (adjacent to DRV) to drive INPUT- OK. what I don't understand are the GROUNDS the manual says:"The twisted pair shield should be terminated at the7I33 ground and left un-terminated at the drive end. The drives input ground should be returned to the same ground as the controller or PC,"  This is the schematic of the servo driver. 
Wouldn't the ground of the 7i33TA already be connected to the INPUT - input of the maxx 400 servo driver?  
 Thank you.

7I33 DRV -->IN+
7I33 GND -->IN-
CABLE Shield -->7I33 GND
(shield unterminated at drive end)