I know that Roblox' default walk speed is 16. Say I edited my game's default WalkSpeed value to 15 in Roblox Studio > Game Settings > World > Walk > Walk Speed.
In a script, I make the player's walk speed to 0 (stop). After x seconds, instead of setting up the player's WalkSpeed manually, I intend to set their WalkSpeed to the game's default WalkSpeed when they first entered.
Put a local script in starter character scripts (Located in starter player) then just do "script.Parent.Humanoid.WalkSpeed = 20", 0 is the normal walkspeed
also if that doesn't work then you might wanna do "Script.Parent = game.Players.LocalPlayer" or something like that.