Now this is interesting. As the barrier forms, Strange makes a little 'hmm' of approval, watching intently as the spell shapes itself. He can see Yuya's magic inherent in the thing but is a little surprised with he sees his own as well.

Squeezing Yuya's hand again, Strange tries to pour more of his own power into this, attempting to boost Yuya's magic and strengthen it as much as possible. After all, since it seems this barrier is a combination of theirs, he isn't going to half-ass it.

He'll boost Yuya's magic for as long as it's needed. Strange knows that he's a more powerful magician than Yuya (it's not bragging if it's true!) so he'll magically support Yuya for as long as the kid can take it.