Air vent issue in vostro 3590

Hi guys I have recently bought a vostro 3590 . I have seen the device manual where it is specified that the air vent is at the bottom of the laptop. But in my case the air vent is covered with a plastic from inside so no air can enter from bottom . I thought this is a manufacturing defect and I raised a complaint . After 24 hours they replied me that the air vent of this model is not at the bottom but it is at the rear of the laptop. I don't understand if the air vent is not at the bottom then why there is a air vent like design in the bottom which is covered by a plastic like meterial from inside. Can any one having the same model tell me where is the air vent actually situated? Thanks in advance for your answer