TDEE Calculator

Clawsal

Hello

I am 24 yo female, 165 cm (5'5), 63 kg (139 pounds).
Using http://iifym.com/tdee-calculator/

As I am right now - sedentary - my TDEE is 1656 kcal, which seems correct for me.

However, let's say I start exercising: 3 times a week, 1h. My TDEE jumps to 1898.
That is a 242kcal increase a day. 242*7/3= 565kcal per exercise session. It is a lot! (And I certainly don't spend 565kcal per session of exercise).

What gives?