You should be fine. It seems like if it can be slid into the seatback they'll let you keep it out of your bag. I think I recall hearing there was a weight limit of 2lbs which I have to think your tablet is below. Detaching the keyboard would almost certainly ensure it's okay. I have a small Lenovo laptop that weighs about 2.5lbs that I rarely am asked to stow and it's got a permanent keyboard. I'll often just throw it in the seatback when they are "hawking" just before leaving the gate then pull it out just to be sure.