Original questions hard to read but.
Assuming you have a 50 amp RV (if you have a 30 amp skip to Assuming you have a 30 amp RV)
The adapter you plug into the 30 amp box feeds BOTH sides (hot leads) on the 50 amp outlet from the HOT lead (one hopes) Neutral and ground are passed through.
Your Surge guard (50 amps) does not care if the two legs are the same or different so it works normally either way and passes power through exactly as it does when plugged into 50 amps.. In fact one function of it works BETTER on 30 amp but .. Well,, This is not a proble (obviously).
If you have a 30 amp RV
Then the adapter picks a side, Depending on who made it it will be either the left or right (This assumes neutral is at the top) side, but in truth, NORMALLY it does not matter.. Again the surge guard works exactly as it would on a 30 amp site.
NOTE: I do recommend having 2 adapters if you have a 30 amp rig.. one which passes the Right side through and leave the left disconnected, and one that works the other way around.. From time to time (Rare but it happens) one might work better than the other.
Plus. with 30 amp Rigs.. A spare adapter (and a spare plug) are recommended anyway.