If you have a commit associated to a single Jira issue, and as part of the commit's body you have references to multiple other issue keys, Jira will read all those issues keys and and display this this commit under the development panel of all those issues.

Please improve this integration and allow the customer to choose if Jira will read all issues key or just the first one.

As a workaround, you can change the unrelated issue keys to lower case, Jira will just ignore those issues keys.

Note: It is the same for pull requets, branches, etc.