Why {creative} attribute is not getting replaced by the Ad ID when using a tracking template?

Hello,
I'm new using Google AdWords API, and we are building an intermediate layer to collect some statistics for the Ad Clicks.
We are trying to add a tracking template URL to an Ad, and using some attributes, something like:
http://www.example.com/?url={lpurl}&cid={campaignid}&gid={adgroupid}&adid={creative}

When I click the "Test" button, it all the tokens gets replaced by the right value, except for the {creative} token does not get replaced by the Ad ID and it gets replaced by 0

What are we doing wrong here?

Thanks,

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