Mathematical language is just not perfectly understood by many people. People could mistakenly use "every month average" when they actually want the 'average per 30 days' but that doesn't change the meaning of those conditions, equally as people composing about "stationery cars" does not change the meaning of "stationery" https://financefeeds.com/oracle-orcl-shares-surge-24-in-a-record-breaking-week/