Once the engine starts, with the amount of oil circulating around the engine, the level of oil in the sump will reduce to a normal level.
Many years ago when it was common to have petrol pump attendants, a colleague recalled that he used to work in a petrol station and made a fortune in commission from oil sales. While filling the vehicle he would ask if he could check the engine oil level. With the engine having just stopped and the oil not yet returned to the sump – he was able to convince many drivers that they needed an unnecessary top-up at an extortionate cost.