How long had he been waiting for? Not long, only a couple of minutes, and Toby had to wait the full fifteen minutes before moving on. Whiiiiiiiiiich meant he had loads of time to chop up the peppermint. He had a sprig of the stuff out already, and now cast 'scourgify' on both sides of the knife blade and started to chop up the peppermint.
He perhaps wasn't quite so focused on the task as he should have been, finding his attention would occasionally wander to others around the room. Unwise, perhaps, when you were wielding a sharp knife designed for chopping up Potions ingredients. Luckily, though, there were no disasters to be had (except he might have completely missed the mint at one point and nicked his hand with the blade instead but shhhhh) and Toby soon had a completely chopped up sprig of peppermint.
Toby inspected his TOTALLY OKAY (sorta) hand while he waited for the rest of the time to tick down, before remembering it was wise to watch the progress of his potion instead. The colour change of the liquid in the cauldron was already well underway, and Toby watched as it continued to turn into a cool grey colour. When the fifteen minutes were up, Toby noted that the potion was indeed good and grey, and added the chopped up peppermint.
Now that he was pretty much done, Toby started packing away his potions kit and ingredients and everything, clearing up and cleaning as much stuff as he could without disturbing the still brewing potion. He glanced at the bubbling liquid from time to time to see how the colour was doing, and when it did indeed turn white he extinguished the flame, picked up his pre-cleaned vial and ladled some into it to hand in. After attaching a label that read '
Toby Fuller-Thompson, Hufflepuff, Sixth Year' he went up and left it on Professor Culloden's desk, but didn't look at him quite yet. He was still... sore from that early mistake. And maybe worried that Culloden's opinion of him had been affected because of it.
Returning to his desk, Toby updated his notes one more time, making sure to get everything down that had been written up on the blackboard. Once he'd done that, he shoved his notes in his bag, which he slung over his shoulder, and headed for the door.
"Thanks for the lesson, Professor Culloden," the Hufflepuff said as he went, giving that usual polite wave of his before disappearing into the corridor.
Though really... he wasn't totally sure he enjoyed the idea of maybe testing this potion for homework. Why was that a problem that kept happening for him in Potions? Sigh.