I don't get it. What the fuck is zepto cash and how am I getting stuff for free?

So I used zepto for the first time yesterday and I already somehow had zepto cash and I used it to order cream. AND I WAS DELIVERED CREAM? WITHOUT HAVING TO PAY FOR IT. And today I ordered stuff worth 110 and I again magically had 125 zepto cash ???? And I was delivered this stuff again for zepto cash without having to pay anything. WHY IS ZEPTO GIVING ME FREE GROCERIES WHAT IS ZEPTO CASH