I think he refers to this: https://www.keycdn.com/support/how-to-u ... ee-domains
In the case of OpenCart there is nothing much you can do to improve performance when it comes to the usage of cookies.
Sites like gtmetrix come up with all sorts of generic recommendations which you can safely ignore.
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But I've sent him the Mod by PM, so, the problem should be solved by now, I assume.
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