Comparators still giving off power when hopper inventory is empty

1. Place hopper down and have a comparator coming out of it into a redstone line
2. Place between 1-63 items in hopper and leave one of that item in your inventory (make sure there's no other of that item in your inventory)
3.double click on that one item in your inventory to 'grab' the items from the hopper.
4.until the comparator is updated the redstone will continue giving off the same redstone signal it was before.