The claim that millions of carbon-14 measurements have been made globally is a matter of common knowledge and everyday scientific observation, given that radiocarbon dating has been used extensively across archaeology, geology, and environmental science for decades without requiring a specific citation.
The claim states a broad, obvious, and uncontroversial global aggregate fact about scientific activity. Millions of radiocarbon measurements have been performed worldwide since Libby's discovery of the method in the mid-20th century, rendering the claim common knowledge. Therefore, no citation is needed, and STEP 0 applies to classify it as such.