Oh dear, it was the decision of the Police at Selhurst to restrict numbers, FACT
Not sure it's the same with your club though, I think they might be being petty, unless of course you can evidence that the police have restricted numbers at the Amex.
No pettiness at all and no specific restrictions on your allocation at the AMEX. You will get the maximum League match away allocation - minus perhaps a slightly bigger buffer zone insisted on by the ground safety people - just like any other league team would.
There will be no other spare seats available to give you - all will be sold - although no doubt some of you will be in the 1901 corporate hospitality, winding up those in there.
I imagine if your behaviour is poor though, you potentially could have a reduced allocaction next time.