Keto questions

Hey everyone. I've been looking into keto diet information for a couple weeks now and have a few questions. I'm 6'6 and around 300 pounds, and I'm wondering if the 20 grams of carbs a day is based on a 2000 calorie diet? With my activity level (daily light yoga, 2 hour dog walks, low intensity lifting 4 days a week) I can consume around 4000. Does my carb count then double? Or should I stay below that 20 gram level any way? I know that calories don't fit perfectly in this discussion, but this is the best way I can think to ask the question. Thanks everyone