Clovis told CNN's Alisyn Camerota on "New Day" that he's not sure where Pierson got her information, but said the campaign is "fixing it."
The issue arose the day before, when Pierson was on "New Day." While Pierson was admitting that she had been wrong in alleging President Barack Obama and Hillary Clinton were responsible for the death of Capt. Humayun Khan in Iraq in 2004 -- well before Obama took office or Clinton was in the administration -- she sought to defend herself with statistics that were also incorrect.
"That's why I used 'probably' (about their responsibility), because I was just going through the time line," she said. "Because since then, we have had tens of thousands of soldiers that have been lost. One million wounded."
In fact, the numbers are far different than Pierson's assertion. According to the Defense Department's casualty report
, 3,481 military personnel were killed in action during the Iraq War, from March 2003 to August 2010, and 31,925 were wounded in action.
In Afghanistan between October 2001 and the end of 2014, 1,832 military personnel were killed in action and 20,030 were wounded.
If you include all deaths, military and DoD civilian, the numbers of dead are 4,424 and 2,349, respectively, in each conflict.
Together, that adds up to less than 7,000 killed and roughly 52,000 wounded.
Clovis said he doesn't know where Pierson got her information, but said "facts are important."
"I think we're fixing it," he said. "I guarantee it that won't happen again with her, that's for sure. And it won't likely happen with anybody else, because when you do go out, you have a responsibility."
He added: "I think it is important to come on here and have accurate information, and present our case in the best possible way we can. And to be as firm and assertive as we can be. And I think facts always help you, the truth always helps you, and I think that's always where we ought to be."