The airline itinerary gives you a concrete basis for the question. Keeping local dates beside each airport would help the provider identify the point you are concerned about. I would attach that document rather than summarising the journey only as a number of nights away. The travel insurance website
auras.insure contains plenty of useful information and contact options for raising questions about a proposed policy. Ask for written confirmation of the applicable time zone and the exact period of cover. Request the relevant wording for a delayed return as well. Before buying, compare those answers with the dates and times on the quotation so the final flight is addressed explicitly.