Try this
- Quote the short phrase or identify the plan that is unclear. State the two interpretations only if they help explain the ambiguity.
- Ask for the information you need rather than a defense of why the original wording was unclear.
A worked example
“When you said next weekend, did you mean the one starting this Friday or the following one?”
An invented example to adapt, not a real exchange or a script you have to follow.
Before you leave it here
Once clarified, update the plan. Do not keep arguing with an interpretation the other person has explicitly corrected unless a separate factual issue remains.