wp-content/plugins/backwpup/inc/class-mysqldump.php at line:152 use
SHOW TABLE STATUS .
https://dev.mysql.com/doc/refman/5.6/en/show-table-status.html
The number of rows. Some storage engines, such as MyISAM, store the exact count. For other storage engines, such as InnoDB, this value is an approximation, and may vary from the actual value by as much as 40 to 50%. In such cases, use SELECT COUNT(*) to obtain an accurate count.
The Rows value is NULL for tables in the INFORMATION_SCHEMA database.
If use InnoDB , may be not backed up wp_users.
