I recently discovered a have an item "Boots_LeatherB" that has a "+?" enchantment. Problem is, I don't remember if I put the enchantment on them or I thought it was +7 when I equipped them. Just something to note
I came across the same issue later yesterday, but only happened after the new clothing or weapon got enchanted with extra defence/attack.
It doesn't seem to affect clothing and weapons that are found enchanted from chests, for gloves it displays the correct spell bound to them, either found or done by the player.