A Cash Out value is calculated using amount staked, price at the time the bet was placed and current price at the time of the Cash Out. While you may have most selections winning, if one or more selections are considerably longer odds than taken to win, it will have a large impact on your cash out value.
To calculate your potential payout on an underdog, all you need to do is multiply your stakes (the amount of money you wagered) by the value resulting from the moneyline odds divided by 100. Put simply: Potential profit = Wager x (Odds/100).