Days since last comment field not displayed correctly in filter subscription e-mail

I have a filter that includes the custom field "Days since last comment" (from the Toolkit). All comments are set to security for group "Staff. When displayed on screen, in issue navigator, the value is displaying correctly. But when the staff members receive a filter subscription, the value is not displaying correctly. I think it goes back to the last comment that was visible to all users.

So, when they receive the email it shows last commented 8 weeks ago when there have been numerous comments in the past few days. It is misleading. I am logging the issue here rather than JTOOL because the problem is with the filter subscription logic, and not with the custom field itself (which displays correctly in issue navigator).