Exporting issues size is 15MB but max is 20MB

Summary

Exporting issues size is 15MB but max is 20MB

Steps to reproduce

1. Open https://gitlab.com/gitlab-org/gitlab-ce/issues
2. Click Export as CSV button
3. Check the mail the size of attachment exported is ~15MB
4. But the max size limit is 20MB

Example Project

https://gitlab.com/gitlab-org/gitlab-ce

What is the current bug behavior?

All issues are not exporting because of size issue

Output:

This attachment has been truncated to avoid exceeding a maximum allowed attachment size of 20MB. 9719 of 14513 issues have been included. Consider re-exporting with a narrower selection of issues.

What is the expected correct behavior?

Issues must be exported upto 20MB

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com