I can understand your concerns....
With the 50A Receptacle 'upside down' ie: GROUND at bottom vs at top the Surge Guard plug is upside down so it doesn't hang straight down
50A is hard to screw up voltage wise ---unlike 30A which can be 120V or 240V
50A ...2 hots, 1 Neutral, 1 Ground
SOoooooo
Turn the two 50A circuit breakers OFF
Pull Receptacle and reorient it so the GROUND is at top (then surge guard can plug in and hang straight down)
To reorient....remove wires/rotate receptacle/connect wires
Hot on each side (Black/Red Wires)---Neutral on bottom (White Wire)---Ground on top (Green/Bare Wire)
Then plug in Surge Guard then after it completes testing and allows AC Power use it