Is 0 caffeine decaf tea possible?

Are decaf tea that claim to have 0 caffeine real? I saw several [decaf tea from Harney and Sons](https://www.amazon.com/Harney-Sons-Vanilla-Comoro-Decaffeinated/dp/B000R32F6M/ref=sr_1_8?crid=31QF0HKQAW1X4&keywords=vanilla+comoro+harney+and+sons&qid=1699771934&sprefix=Vanilla+com%2Caps%2C149&sr=8-8) that has “0mg caffeine” on the packaging. Is this true or marketing bs?