As you can filter queries by sources this means comments on a publication may be different numbers. Let's look at an example:

Josh does a post on APP2
Sally comments on APP3
John comments on APP4
Paul comments on APP2

Josh's post has 3 comments but across many apps. When you filter on sources you only bring back the sources from those apps. This example below its showing you how we get publication ID 0x01-0x01 and we get back the number of comments that have been done on the app your_app_id. This allows us to get the correct counters etc.

API design

query Publications {
  publications(request: { publicationIds: ["0x01-0x01"] }) {
    items {
      ... on Post {
        stats {
          totalAmountOfComments
          commentsTotal(forSources: ["your_app_id"])
        }
      }
      ... on Comment {
        stats {
          totalAmountOfComments
          commentsTotal(forSources: ["your_app_id"])
        }
      }
      ... on Mirror {
        stats {
          totalAmountOfComments
          commentsTotal(forSources: ["your_app_id"])
        }
      }
    }
  }
}

{
  "data": {
    "publications": {
      "items": [
        {
          "stats": {
            "totalAmountOfComments": 3,
            "commentsTotal": 1
          }
        }
      ]
    }
  }
}

Using LensClient SDK

const result = await lensClient.publication.stats(  
  {  
    publicationId,  
  },  
  ["your_app_id"] // sources
);