"I just need one, but fair warning, it does go in the potion, so that one you wouldn't get back," he told her. "You won't be able to taste it, though. As for how long it lasts...it's temporary. About a week or so. You could keep taking it as long as you wanted to, but one dose lasts about a week."
He jotted another note in the margins. This one would need a bit of tweaking, but Alex was a bit like a chemist with potions. An adjustment here and there almost always ended up working in his favor.
"Alright, here's what I'll do," he said after a moment. "This has to brew for a few more hours, then I'll clean it out and get to work on yours. Give me about a day or so, and it should be done. Will that work?"