Zomato charging different delivery charges for same distance

I tried to order a 2 different 99 Rupees dishes in a restaurant 2.5km away. It gave me delivery charge of 26 Rupees. But when I remove one 99 Rs dish and reduce the order value, suddenly the delivery charge increased , almost doubled for the same 2.5km distance This is unfair because the distance is same. It looks like the company is trying to increase the order value with such tricks although they have a platform fee of 10 rupees