Hope I understood the question...
Actually, I meant if you can see more than 5000 unhandled reports, all being made in less than 30 days. Imagine someone reporting 1000 posts / day for 10 consecutive days and, for some reason, they are not handled. That user can see only his last 5000 reports. But can you see all 10.000 unhandled reports?
If a report is not attended by any mod and after the specific time period, 30 days or what ever, receives the "unhandled" status it is no longer displayed in any report queue. Only the user that reported the post can see it in his/her report history or maybe theymos in the db. It magically vanishes from the mod report page.
About that, also the user can not see anymore the reports older than 30 days. They disappear also from user's posting history, not just from mods' queue...