By following the application link and pulling up the "**Offer Details" overlay I found:
Statement credit(s) will post to your credit card account the same day as your purchase(s)
It seems clear they anticipate the possibility of more than one charge per day. It is not clear, however, whether they will allow more than one credit per flight segment, but given that they charge $8
per device, I would have to think they cannot tell the difference between one passenger with two devices and two passengers with one device each.