Hi Aubie,
Career Earnings are a cumulative total of credits won in tournaments, credits earned through tier promotion, sweepstakes prize winnings and tournament prize winnings. For example, the #1 player on our money list right now won a trip to this year's Open at St. Andrews.
To check the amount of credits you have to spend, simply look in the top left hand corner of the friend widget. Under your name it displays your tier rank and your scoring average. Just to the right of that is your Credit amount and that indicates how much you have available to spend. You can also find this information by clicking the ACCOUNT button on the friend widget.
Credits can be used to purchase club upgrades in the Pro Shop or enter premium tournaments. You can also wager your credits in a Match Play Challenge against another player or participate in the Ready Go Tournaments. (please note that both Match Play Challenges and Ready-Go's are void where prohibited by law)
Your $1.58 comes from a 50c tier promotion from Hack to Amateur and a 100cr tier promotion from Amateur to Pro. The remaining 8 cents is from your tournament/CTTH winnings that you have received through the course of play.
For more information about the game, please be sure to consult the Help/FAQ at the bottom of every WGT page.
Thanks =)