Hi Andriej,
Have a look at the parameters at Production control > Setup > Manufacturing execution > Production order defaults

I thought that Maximum report quantity had an effect when the RAF is done by the Warehouse mobile device, but in a quick test I did, it did not. Maybe you will have better luck!
However, the Accepted surplus in production is considered by the mobile device:

It allows you to specify a maximum over-RAF percentage. Even if you put in 100% (double the production order quantity), I'm sure it would block your example 1234567 quantity.