Not sure why there isn't an adjustment for this on the Adjustment's tab, but seeing as how surprise is a Condition in 5e and not a special round of combat, there should be an adjustment for it on the condition list in the adjustment tab.
5e SRD, p. 90
"If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends. A member of a group can be surprised even if the other members aren’t."
5e SRD, p. 90
"If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends. A member of a group can be surprised even if the other members aren’t."