The pic seems to show one pos (lower left battery) as + and another pos (upper right battery) as -. That ain't right.
But whatever...the rigging in that pic is not a SmartGuage "Method 2" rig. In a Method 2, all four negs are tied together in a line, and the same with the pos.
You need to add a jumper from say upper left battery neg, to lower left battery neg. That completes the four-in-a-row neg line.
Then re-rig the pos to jump upper left battery pos to upper right battery pos. Then upper right battery pos to lower right battery pos. Then lower right battery pos to lower left battery pos (remove lower left to upper left).
The your neg connection would be upper right battery, and your pos connection would be lower left battery.
(Someone double-check me on that...my brain just turned to mush scrolling up to the pic then back down to the text edit box on a phone...about a hundred times.)