I bought this liquid from everything liquid in the uk and the bottle looked light. So i weighed it and it was 233g. If i am correct 250ml is 250g. 17ml short is such a odd number that i have never had before. This is there response.
How so, the OP is looking for an answer. Inquiring from the manufacturer what the specific gravity is sounds like a reasonable request, they may just be a mixing house but it wouldn’t hurt to ask, the email states “If you need any further information…”