Net profit

A company’s statement of profit or loss for the year ended 31 December 20X5 showed a net profit of $83,600. It was later found that $18,000 paid for the purchase of a motor van had been debited to the motor expenses account. It is the company’s policy to depreciate motor vans at 25% per year on the straight-line basis, with a full year’s charge in the year of acquisition..
What would be the net profit after adjusting the error?
sir here why are we adding 18000? it should be subtracted because they considered it an expense so expense should be subtracted from the net profit? please explain the concept here