Estimated wins

Because that's your estimated wins. Based on pure statistics, by how many giveaways you've entered, and what the chances of winning each were.

It's in the FAQ.

Your EW is based on your chance to win each of the giveaways you've entered. Most of the time, people tend to win close to the number of games listed in the EW, although winning can come in spurts.

From my Guide to winning

Estimated Wins

This is a number calculated by the chance you had of winning each giveaway you have entered. If you entered a giveaway with a 50% chance of winning, your Estimated Wins will increase by 0.5, no matter if you won or lost. This number is no indication that you should have won that many games, it is simply to allow you to see if you are more or less lucky than what the odds allow.