Hopper duplication bug

When I threw any item/block into a hopper which directly put them into a chest below, it duplicated the items in a weird pattern. Here are the results(',' separates each throw with 1 item/block):

'CREATIVE'

Redstone dust:
2, 4, 5, 6, 7, 8, 10, 12, 14, 16, 17, 18, 19, 20, 22, 23, 25, 26
Redstone torch:
2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 16, 17, 18, 20, 22, 23, 25, 27, 29, 31, 32
Torch:
2, 4, 5, 7, 9, 10, 12, 14, 16, 18, 19, 21, 23, 25, 26, 27, 28, 29, 30, 32
Grass block:
2, 4, 5, 6, 8, 10, 12, 13, 15, 17, 19, 21, 22, 24, 26, 28, 29, 30, 31, 32

That's what I tested. Really weird. From 64 grass blocks to 75, From 64 torches to 76.

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'SURVIVAL'

Redstone Torch:
2, 4, 6, 7, 8, 10, 11, 12, 13, 14, 16, 18, 19, 20, 22, 23, 24, 26, 27, 28, 29, 31, 32
From 64 to 73 redstone torches

Torch:
2, 4, 6, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 19, 20, 22, 23, 25, 26, 28, 29, 30, 32
From 64 to 73 torches (Here's a pattern!)

Redstone Dust:
2, 3, 4, 6, 7, 8, 9, 10, 11, 13, 15, 16, 17, 19, 21, 22, 23, 25, 26, 28, 29, 31, 32
From 64 to 73 redstone dust

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