Mathematical language isn't well understood by many people. People may mistakenly use "regular monthly average" when they really want the 'average per 30 days' but that doesn't change the meaning of those conditions, just as people writing about "stationery cars" does not change the meaning of "stationery" or "stationary". https://financefeeds.com/under-70-or-over-100-dollars-octa-broker-analyzes-oil-market-under-the-tension-in-the-middle-east/