Bitshifting With BPF in wireshark

[asdfdsfds <angelofthedark () windowslive com>]

Hi, Write I have a question about BPF,
I have the following filter

tcp [((tcp [12] & 0xF0) >> 2): 4] = 0x12341234

My question is the following
(tcp [12] & 0xF0) >> 2

the bitshifting is performed clockwise to multiply the result of

(tcp [12] & 0xF0)

2 ^ 2

Why bitshifting is the right and not the left?

I saw filters where the IP header is made to the left as it should be .

thansk!.
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