This is asking you if the Android Operating System can use the Audio Jack when trying to process a credit card payment when a swiper is plugged in.
Tap "Allow" in order to allow permission to use the swiper, seeing as the swiper uses the audio jack to transfer the credit cards information.
Note: Tapping "Deny," will prevent you from using the card reader.
This indicates that you cannot process credit cards using the Audio Jack/Swiper. You will need to try again or go into the settings of the device to re-enable the Audio.
