NFL gave Vilma a sworn affidavit from Gregg Williams stating Vilma offered $10k to knock out Favre

As someone posted in the comments section, The NFL is going to picked what it believes in the Gregg Williams' statement. They believe him when he said Vilma offered 10,000 dollars but they don't believe him when he says it was a pay for performance. How can only part of the declaration, not affidavit, be true? I wouldn't believe Greggg Williams or the NFL if they told me water was wet.