This can happen if your data source is configured to retrieve certain breakdowns, specifically the following:

With these breakdowns, a user can be part of multiple categories, so any clicks/costs/impressions associated with the user are attributed to all categories that the user is part of. As a result, all metric values will be inflated, often by a significant amount.

For example, if a user with an interest in "cars" and "boats" clicks on your ad, you will get one click for the "cars" interest and one for the "boats" interest in your report.

To import LINE Ads data that accurately reflects the totals for your ad account, we recommend connecting a data source on Ad level.

We currently do not support custom conversions in our LINE Ads integration, but we are looking into ways of implementing them.