Answer:
He doesn't believe the Colonel is trustworthy, so he offers a test he knows he'll fail.
Step-by-step explanation:
So, he was a former slave along with his wife before everyone was freed. His old "master" basically sent him a letter saying that he would pinky promise to treat him well, that he would be free, and that no one else would give him a better opportunity. At this point, he's earning decent money, has a fine life, and knows the Colonel is a not so great guy. He tells him he isn't mad about the Colonel trying to shoot him 2 times, or any of the other mistreatment, but he wants the Colonel to prove he's changed. He wants the $25 a month he should have been paid for working for him for 32 years, and the $2 a week his wife would have made in 20 years. It ends up being over $11,000 - which he knows the Colonel would never pay.
Also, come on guys - you're better than flooding this site in fake answers. Don't you have anything better to do with your time?