Potential witnesses who may testify at the Nation's second land claim trial in July has nearly doubled, from seven to 13. That number was submitted to U.S. District Judge Neal P. McCurn of Syracuse by the July 16 deadline. In the non-jury trial McCurn will decide whether to adjust the jury's Feb. 17 award of $36.9 million in damages to the Cayugas. He also will consider whether interest should be added to that award, if the state acted in good faith and if there should be an adjustment because the claim was not filed until November 1980. The tribe brought suit nearly two decades ago, seeking return of some 64,000 acres in Cayuga and Seneca counties. Both the Justice and Interior departments have intervened on behalf of the Cayuga.