No such thing. Take another look. There is no estimated earnings. It just shows you the balance of anything in your account. You get paid once per month, with the payouts beginning around the 8th. Once they begin, payouts can take anywhere from between a few days to a few weeks. You can always track the status at Ads Payout Status Update
It’s showing you have no balance, meaning you probably just linked your account. Either that or you’ve already withdrawn the balance.
-NOTE-
You haven’t seen a lot of ads. Even when it pays, you won’t get much. At most you’d be getting about 0.375 BAT based on the ads you’ve seen. But I’m going to bet a lot of those are House Ads, meaning it will be even less.
And if you immediately sweep that to your ZebPay, you will have to transfer it out immediately or lose it all due to the monthly maintenance fee that they have (make sure no balance is kept in ZebPay by the first of the month unless you are doing bigger transactions to avoid the fee).
Other Note
You may also want to read through information below. While not specifically relevant to your topic, it does contain a lot of helpful information about Rewards which you may want to know.