I think you mean, "I think because of the covid-19, exports will not reach 40% of the country's revenue." The sentence I wrote means that exports will probably be less than 40% of the country's revenue. If you just say "not account for" it is a little ambiguous. Exports could be above 40%. Same with "not represent". "Make up" is more like "reach" but "reach" is more precise, in my view." You might mean something else entirely. If so, be more specific with your question. Of course, if the revenue total depends on the export total, then the revenue will decrease when the exports decrease, but not proportionally.