Search api returns incorrect total issue count

Hello, I’m wondering why this Github rest search issue call is not returning the correct total issues count:

https://api.github.com/search/issues?q=repo:mui-org/material-ui%20is:issue

returns: "total_count": 12674

In the UI:
issues

12289 + 471 = 12760

Using Graphql API it returns the correct count when I use the repository connection:

{
  issues: search(type: ISSUE, query: "repo:mui-org/material-ui is:issue") {
    issueCount
  }
  pr: search(type: ISSUE, query: "repo:mui-org/material-ui is:pr") {
    issueCount
  }
  repo: repository(owner: "mui-org", name: "material-ui") {
    issues {
      totalCount
    }
    pullRequests {
      totalCount
    }
  }
}

Output:

{
  "data": {
    "issues": {
      "issueCount": 12674
    },
    "pr": {
      "issueCount": 12628
    },
    "repo": {
      "issues": {
        "totalCount": 12760
      },
      "pullRequests": {
        "totalCount": 12661
      }
    }
  }
}

What filter am I missing in my search query in order to get the total issue count ?