Difference found between database and vardefs

Hi, I have just installed SuiteCRM 7.11.8 on my server and when I do a “quick repair” it shows me “Difference found between database and vardefs” with this script to execute

/* Table : users /
/COLUMNS/
/
INDEXES */
/*INDEX MISMATCH WITH DATABASE - idx_user_name - ROW idx_user_name index [0] => ‘user_name’ [1] => ‘is_group’ [2] => ‘status’ [3] => ‘last_name’ [4] => ‘first_name’ [5] => ‘id’ /
/
VARDEF - idx_user_name - ROW idx_user_name index [0] => ‘user_name’ [1] => ‘is_group’ [2] => ‘status’ [3] => ‘last_name (30)’ [4] => ‘first_name (30)’ [5] => ‘id’ */
ALTER TABLE users DROP INDEX idx_user_name, ADD INDEX idx_user_name (user_name,is_group,status,last_name (30),first_name (30),id);

If I execute it SuitCRM shows me “Database and vardefs are synched” but if I do another quick and repair it shows me again the same message with the same script to execute.
What could be the problem?

There are a few threads about this already, for example this one

https://suitecrm.com/suitecrm/forum/suitecrm-7-0-discussion/27256-quick-repair-keeps-saying-differences-found-between-database-and-vardefs

What if I just let it be and do nothing?
I don’t mind seeing the message every time I run the quick repair.
Thank you.