Apple has had issues with the Retina MacBook Pro (LG display) iPad 2nd gen - 4th gen (lg displays), and iPad mini (lg displays). Now not all panels exhibit this and the image persistence has been addressed on the MacBook pros by replacing the defective screen (Samsung panel) or newer LG panels have had the defect resolved. It seems to stem from poor electrical conduction and holding a residual charge. I'm sure other manufacturers have had this happen, and it does dissipate after a few minutes. But it's aggravating none the less. LG is hit and miss in this regard and Apple is the king of hiding these facts from consumers and never owning up, but just replacing without acknowledging fault.
Now the new MacBook Pros don't seem to have this issue with LG screens but some current iMacs have and the iPad minis continue to. Likely a yield issue and they are trying to meet quotas. But with their own logo on the device, I'd assume they are cherry picking the screens. Either way, try the device and before your return period is up, put a solid grey image on after you've had something else open for 10 minutes and you can see if its doing it or not.