Durham plans to file two 404[b] disclosures with the court on Monday.  

What that means is that it appears Durham is claiming he has at least two more examples he intends to use  to demonstrate Sussmann’s character that he intends to file. Examples where he can prove Sussmann did something illegal or wrong. 

In a case like this, about the defendant lying to a federal official, other examples of the defendant lying to other people helps the prosecutor establish his case.  

Naturally Sussmann’s lawyers are going to file to try to prevent Durham from providing these two examples during the trial.