Interesting as a typo would not necessarily be an ambiguity but it certainly sounds like an inconsistency and it should be treated as such. Clause 17.1 confirms that either Party should notify the other of such an ambiguity/inconsistency and the Project MANAGER should issue an instruction to resolve (clarify) it… If this subsequently satisfies a reason for being a compensation event within 60.1 then 63.8 comes into affect, which says it will be assessed in favour of the Party which did not create the ambiguity or inconsistency.
Glenn is absolutely right in what he says if it is a inconsistency in the Works Information but, as you say, it is in the Z clauses which I am assuming the Employer effectively wrote. (By ‘effectively’, I mean it may have been a consultant but as far as the law is concerned it’s the Employer).
In this case the contract is silent so we have to look to contract law, where what used to be called the ‘contra proferentum’ rule applies. What does that mean ?
Quoting the Wikipedia definition “Contra proferentem (Latin: “against [the] offeror”), also known as “interpretation against the draftsman”, is a doctrine of contractual interpretation providing that, where a promise, agreement or term is ambiguous, the preferred meaning should be the one that works against the interests of the party who provided the wording.” In this case the Employer.
Without bringing in lots of other legal ‘Rules of Interpretation’, it should be noted that this is where there are two reasonable readings as opposed to, at its extreme, a deliberate misinterpretation using rather tortuous logic.
If a typo is clearly a typo and is clearly demonstrable as a typo then it will be corrected as a point of interpretation of the contract or, if necessary, rectification of the contract. That it creates an “opportunity” later for one party is less relevant. An objective legal test will be applied.
The legal issues may be quite tortuous but the result will almost certainly be that the typo is corrected or ignored…