Material Document with wrong value

Dear All

When I to do a good receipt with the movement type 561, the system create a material document with incorrect rounding value.

For example:

Good Receipt  MVT 561 in.entry balanc.

Quantity 6.000,000

Material Price 6.601,67.( Price unit 10000)

So the value should be (6000/10000)* 6601,67. = 3961,002 ( currency CH) while the system report the value 3961,02.( currecy CH)

I don't understand because  the system loses a decimal

Thank you so much

Regards