They mean they will only make 500 vehicles of this model. However, quite often they make a design change, call it a different model, and do another limited pro

They mean they will only make 500 vehicles of this model. However, quite often they make a design change, call it a different model, and do another limited production run. McLaren did exactly this with their '675LT' model. The initial production run was 500 cars which proved very popular and sold out the day they were announced. However there was still much demand for the car. So McLaren made a convertible model of the car and named it the '675LT Spider' and did another limited production run of 500 cars. This behavior is not limited to McLaren. Bugatti is very guilty of this, they've ran at least 4 different 'limited production runs' of their Veyron.