Calculation issue

[MykelSilver]

I have two miners
Miner A hashes at 6 GH/s (approximately)
Miner B hashes at 400 MH/s (approximately)

I would expect the number of shares of Miner A is 15x as big as the number of shares of miner B
In reality the number of shares of miner A is only 4.2x as big that of Miner B

Anyone knows why?

In the image below the number of shares for each miner can be found at the Round column

[MykelSilver]

Answer: The diff of Miner A was 4 :-)