Went to add a command for my NPC that adds tags to players within a 5 block radius of said NPC

/tag @p[R=5] add RealmInfo (Set to a button named I Understand)
Also attempted using just @p without the radius, same result just adds the tag to everybody instead of the closest player.

Upon using the NPC and clicking the button, instead of adding the tag to the nearest player and ONLY the nearest player, it adds the tag to every player in the game.

tested using
/tag @a list
shows 2 Entities with the tag, but only one of the players were nearby.