"Blended" implies different mash bills mixed together. It's all mixed from various barrels, unless it specifically says "single barrel". That process is called "batching" and they will add what they need to to hit the flavor profile. The youngest constituent age is what has to be listed on the bottle.

https://thewhiskeywash.com/whiskey-styles/bourbon/lets-demystify-whiskey-bottle-label-age-statements/

https://www.bourbinsane.com/bourbon-batch-variations-explained/