Ignis would chuckle himself if he wasn't terrified of the situation they were in. He doesn't need an explanation- at least not right away. They probably won't have a lot of time for it either if memory's about to come to an end soon.

"Well, apologies, but you do have to wake up from the memory." Or you will end up floating in Dream Width and Ignis is going to lose it.

"You came for me when I was lost and I woke up when memory ended. Thank you." If he has to guess, the similar will happen with Noct's memory. "I'm glad I managed to reach you in time..."