He's listening intently as Billie explains, making mental notes as he does so. Wrist and forearm stiff, throw it straight, don't try to be theatrical with it. When it's finally his turn, Strange nods. There's a pause before he throws as he's very obviously trying to remember everything Billie taught him, adjusting his arm, his wrist, his position, all of that before he finally throws the knife...

...and forgets that he needs to put a little upper arm strength into the actual throw. His form is halfway decent! But that doesn't mean shit when the knife arcs downwards and lands on the ground about two thirds of the distance it's supposed to go.

"...that one didn't count," he arbitrarily decides, as he walks forward to pick up the knife, hoping to the heavens that Billie doesn't notice him blushing.