Mailbox size nearing quota but only 27% found??

Mailbox size nearing quota but only 27% found??

I keep receiving emails stating that the mailbox is nearing quota:

Current Storage (including the storage utilized by POP Accounts) : 5,088 MB
Allocated Storage : 5,120 MB

I followed the steps found here:
https://www.zoho.com/mail/help/mailbox-quota.html

I deleted all emails previous to Dec 2015.  When going through all folders, there's a synopsis of the folder like below, of which can only account for 27% of the quota.

(This is the inbox)
Storage Details
Folder (17%)
This account (97%)
Allotted (5 GB)