Items with +1, +2, +3, +4, and +5 durability are the random result of smithing. During the course of playing Syrnia, tools and weapons will break randomly with use and will be removed from the players inventory. Items with + Durability will NOT be removed from the players, but they will simply have the their + Durability reduced by 1.
Soft Spider Silk and Harded Spider Silk can be applied to items to give +1 Durability and +2 Durability respectively. This can be particularly useful when applied to expensive weapons such as Koban Axes or tools such as Obsidian Pickaxes
Items with +0 Durability are NOT errors. Instead they are simply items which have run out of + Durability. Upon breaking, they are removed from a player's inventory just as an item without any + Durability would be.
Items with + Durability CANNOT have spells cast on them or have Soft/Hardened Spider Silks applied to them.