you actually understand this far better than many people! you are running on fat, and you're not in ketosis. it works precisely as you've surmised. 70 grams of carbs gave you 280 calories - ergo you're running on something other than sugar.
your body runs on whatever you feed it. feed it more fat, it burns more fat. feed it more sugar, it burns more sugar. feed it fewer calories than you expend, and it burns stored fat.
keto-adaptation sucks and is completely unecessary. you're doing well!