Mail Migration process suspended

Mail Migration process suspended

Account: testing1@androsentry.com

while performing mail migration, it has been suspended due to mailbox size crossed.
 
But Account storage limit is 50GB. Please let me know what the issue could be.

Details: Your "IMAP" migration scheduled on "Mon, 18 May 2020 07:49:02 +0530" has been suspended, since your mailbox size crossed the threshold limit.