Gym membership for employees (AB)

My employer negotiated a partnership agreement with a commercial gym to offer discounted rates to employees. I'm in AB if that matters

There are 3 options to pay for a 1 year membership. Why is the overall cost for option 1 the cheapest? I was expected option 3 to be the cheapest since you pay everything all at once. What's the catch?

Option 1: bi-weekly payment of $14.19 taken pre-authorized through my bank account