Magic Butter Decarb Box

So i placed 2 oz of small buds and placed in preheated oven. It says back at 250 for 30 minutes. But it took about 20 minutes to reach 250 inside box. So should i bake 30 minutes AFTER it reachs 250 or untill ?

I swear things like these make very simple tasks harder than they need to be. I would assume you would want to go for 30 minutes after the box reaches 250. I just line a baking sheet with parchmant paper, put the weed on top, then fold the parchment paper over it and stick in in the oven, and I've never had any issues. BTW, it's best to chop or grind buds up before you decarb the plant matter.

250F for 20-30 mins. that simple if your going for THC. If looking for CBD's that's a higher temp and time ratio.