Assuming you're talking about an add-on fee for if Stones plays for England. Is there even a clause in the contract that states we will receive payment for an international appearance? No one knows. If there is, how much will it be? Again, no one knows. Could be £100,000, could be £1,000,000. Could be nothing at all.
Its only a matter if time before John Stones gets his England chance.....I'm sure Ben Mansford hinted there was some benefit to BFC, once he gets international exposure.
Ben said (paraphrasing) 'I can't reveal the clauses due to confidentiality written into the deal. I will say that if any BFC fans want to cheer Stones on in an England shirt then that'd be appropriate' Or words to that effect.
Stones will probably play in the friendlies before the World Cup so therefore an England cap, which should kick in any clauses(if any) regarding internationals.