The status 'Stunned' is not explained in the rules.
According to the FAQ 'Stunned' means to fall and stay unconscious for one game turn.
First problem: If a character is fallen, how can he stand up? Is that explained anywhere in the rules? Does it cost one move action or does it cost a part of a move action? Can You stay on the ground (i.e. after recovered from being stunned)? What are the consequences for being on the ground?
Second problem: The status 'Unconscious' is not explained in the rules too. So, what are the consequences for being unconscious? Does the character loose his next activation? What happens, if an unconscious character is attacked? Will a unconscious target be hit automatically (because it cannot dodge or react)?
Stunned falls to the floor and cannot do anything until the next game turn.
You are correct it probably should say somethig like " gets to their feet and recovers at the start of the following Game turn.
From the final proofs
NOTE: If the number of wounds is equal or greater than the Wound value on the “Crippled” side of the character’s card then the character is unconscious. The character remains unconscious until the end of the Mission unless it has a Special Skill that recovers wounds.