Kevin Costner is shedding light on his decision to depart from Yellowstone.

The 68-year-old actor testified Friday during a child support hearing in Santa Barbara, California amid his ongoing divorce from estranged wife Christine Baumgartner. While on the stand, he shared that a "long, hard-fought negotiation" about splitting season 5 into two parts was behind his decision to leave the Paramount Network series.

Costner said he needed to focus on his own Western epic, the four-part movie series Horizon: An American Saga which didn't work with filming Yellowstone twice a year. Costner said he "changed" his schedule to shoot the first part of season 5, adding, "That's a big deal in this world.

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He noted there were "no scripts written" for the second part of season 5 and "they still hadn't finished" the first part of the season at the time. They decided to do "pay or play" which didn't work and he was set to receive $12 million for each part of season 5.

Costner testified that he wanted to return for the sixth season of the Western series but "I couldn't help them any more. We tried to negotiate, they offered me less money than previous seasons, there were issues with the creative…"

Before ultimately walking away, the actor said he made one last effort to come back and told his representatives "have them pay me whatever number, we came up with a number, and they [Yellowstone] walked away.

" He said on the stand he believed that number was $12 million.

"I've been told it's a little disappointing that [it's] the #1 show on TV, I'm not participating," he added.

 When asked if he will receive a payout from the second part of Yellowstone season 5, he responded, "I will probably go to court over it."

Paramount did not immediately return PEOPLE's request for comment.

In June, Yellowstone visionary Taylor Sheridan admitted he was not entirely pleased by Costner's decision to exit the hit series.

"I'm disappointed," Sheridan, 53, told The Hollywood Reporter about Costner's departure. "It truncates the closure of his character. It doesn't alter it, but it truncates it."

In May, Paramount Network confirmed Yellowstone would end after the second half of season 5 (which was slated to debut in November but is contingent upon the as-yet-unresolved Writers Guild strike). There were talks to bring Costner back to film scenes to bring John's storyline to an end, according to The Hollywood Reporter. 

Despite speculation about tension behind the scenes, Sheridan maintained his praise for Costner's work on the series.

"His creation of John Dutton is symbolic and powerful ... and I've never had an issue with Kevin that he and I couldn't work out on the phone," the Oscar-nominated Hell or High Water writer explained.

He also noted to THR that Costner "took a lot of this on the chin and I don't know that anyone deserves it," referencing the reported friction. "His movie seems to be a great priority to him and he wants to shift focus. I sure hope [the movie is] worth it — and that it's a good one."

In February, Deadline reported that Paramount Network was in talks with McConaughey to lead a Yellowstone spinoff while Costner was looking to reduce his Yellowstone schedule to work on Horizon.

Paramount Network later confirmed Yellowstone would end, and that it ordered a spinoff series for the Paramount+ streaming platform. (Paramount+ is home to its various prequel series, including, 1883 and 1923, and will presumably stream the forthcoming 6666 spinoff that's currently in development.) 

The ending of Yellowstone was announced days after Costner's estranged wife Baumgartner filed for divorce after 18 years of marriage. In court documents filed in the Superior Court of California, County of Santa Barbara Friday, Christine, 49, said she "did not pressure" Costner to leave Yellowstone before the split. 

"I have avoided being public about the reasons for our divorce. I have done this to protect our family's privacy. I did not pressure Kevin to leave the Yellowstone show," Christine wrote in the document.