I know, keeping track really isn't that hard, this would be more of a convenience feature (especially when playing from a mobile device). Early in the set when about to batch explore, it would be helpful to see your total acres on the explore screen so you don't need to keep flipping over to another screen to check when to stop. Later in the set if you're still exploring, it'd be helpful to see empty acres, as in whether you have a full BPT of land free, again without flipping to another page.