– Under construction –
Ask the owner of the request if you correctly understood that X is what is meant.
Ask directly after your doubt arose. Even stronger than a first ‘thank you’ reaction after receiving the request.
In any case, don’t decide upon your next action until you’re crystal clear about what is needed to fulfil the request.
So, don’t assume, don’t ditch your doubt, don’t do something because you’ve always handled things like that this way. Don’t delay, just ask.