Google is trying to be more transparent on Google Adsense earnings of publishers. From today onwards, they changed the message “Today’s Earnings” to “Today’s Estimated Earnings” to show you that the earning may change in coming hours. Technically, there is no difference between the older and the new message as Google is not going to change any calculation formulae for this new message. This new message is just for more clarity in terms of earnings. After certain amount of time, message may change to “Today’s Finalized Earnings”.
Nee Message in Google Adsense:
Here is an excerpt from Google’s announcement about this change,
In order to be more transparent about how our system calculates earnings, we’ve added the words "Estimated" and "Finalized" next to "Earnings" throughout your account. Rest assured these terminology changes don’t reflect a change to the way your finalized earnings are calculated. It’s simply intended to give you a clearer idea of what’s our estimation of your earnings and what’s finalized.
So nothing to worry about this new update in Google Adsense. Keep monetizing your blog or site using power of Adsense.