Hi Sarge,
The $1.50 in your career earnings reflects how much prize value you've won to date. Those were automatically added to your account and would show up on the top right hand corner of your friends list. In your case you received 50 credits for your promotion from Hack to Amateur and another 100 credits for your promotion from Amateur to Pro.
The $1.50 in your career earnings is the value of those 150 credits.
Hope that helps =)