[bluetwo]

There is a concept in law that it is the responsibility of the party making the contract to be specific.

For instance, if I hire you to paint my barn red and specify the shade of red, it had better be that red or you failed to meet the terms of the contract.

On the other hand, if I simply specify "red" then any shade of red would fulfill the contract. The lack of detail was my fault.

Depending on how specific they were, you may have been able to do it. Or, you could have sent them a letter telling them your intentions and let them either loop in the lawyer, or, at their risk, ignore the issue.

[willyt]

I believe the principal is called Contra proferentem. https://en.wikipedia.org/wiki/Contra_proferentem

[NetMonkey]

And as I have learned the very hard way, a judge can just decide it doesn't matter and the appeals court probably won't care.

Please don't ever rely on how it's supposed to be - always, always put in clarifying statements and examples in any contract. Everything should be extremely clear and readable by layman, otherwise even things that should be obvious can be devastating.