Enchantment Table Number Key Glitch

Steps to recreate:
1. Open an enchantment table
2. Put any stackable item in your hotbar,=
3. Hover over the enchanting slot
4. Press the number key of the stackable item
5. You only get one.
The rest are deleted.
This works with any stackable item.
This was discovered while playing survival and trying using the number keys to move 64 books to the table..