This would be a bug, most likely caused by the fact that Wood Elves innately get proficiency in Stealth as a racial bonus, meaning Stealth proficiency from a Background does nothing. So the game likely messes up when trying to show what the actual modifier is (Since you cannot stack proficiency. It's a binary thing, you either have it or you don't. The only thing that stacks with it is Expertise which is something Rogue and Bard get to provide twice their proficiency bonus to a skill)
The actual way that skills work is they're primarily influenced by your attributes, with a bonus if you have a proficiency in them (Equal to your proficiency bonus which is +2 until level 5 when it becomes +3 and then at level 9 it becomes +4 and with Rogue/Bard's Expertise it becomes +4, +6 and +8 respectively)
Whatever your associated attribute modifier is will be the main source of skill, in this case for Stealth it will be based on your Dexterity score modifier (+1 per 2 Dexterity above 10 and -1 per 2 Dexterity below 10). So unless you're making your Wood Elf Rogue with 8 Dexterity, they will not have a -1 modifier to their Stealth skill (Most likely you have 16-17 Dexterity as it's Rogue's primary stat, so that would be +3 which combined with your +2 Proficiency bonus would be the +5 you're seeing outside of this bug)
