The display is powered from a 12 V NMEA 2000 backbone, with a specified 10–16 V supply range. There is no separate battery-positive and battery-negative pair on this component. Use an appropriate drop cable and T-piece on a correctly powered and terminated backbone. A 24 V house bank requires a suitable 12 V network supply arrangement.
B&G specifies maximum consumption of 1.8 W and a network load of 3 LEN. LEN is a network power-budget unit, not a three-amp load. Add the display to the backbone's current and voltage-drop calculation with all the other devices. The product's 5 A fuse specification concerns its network supply arrangement; it is not the display's consumption or a reason to fuse an individual data pin.
The canvas therefore exposes a signal/network marker only. The planner does not carry network power through that marker. Include the display's 1.8 W allowance when budgeting the real backbone feed, and do not interpret an unmodeled network load as zero consumption.