Maybe it was a bad idea to offer an opinion on this, since Childermass hadn't really meant for him to do this instead. Yes, fire only going up is dull, but shooting fire at him is — while not dull — kind of dangerous. Where he hadn't been so inclined to move before, one could say he's motivated to it now, because Strange has misjudged the distance.

It isn't until a few seconds too late that Childermass realizes this, however. He assumed the flame would stop short, just the same as Strange had, but then he feels the heat on his face and it's a split-second reaction that saves most of him. He throws himself to the side, the fire snaking over a shoulder instead.

So, he's gone from hanging out idly in the stands watching to throwing himself to the stand's floor, making sure his shirt is only smoldering and not ablaze. Good job, Strange. Excellent work.