How many astr?

I'm curious, could you elaborate on the unit of measurement mentioned in the passage - 'astr'? I understand it's a reference to a unit in the context of cryptocurrency or finance, but I'm unsure of its specific meaning and application. Is it a unique denomination tied to a particular cryptocurrency or exchange? Is it used widely or confined to a niche community? How does it compare to other commonly used units in the space, such as BTC, ETH, or USD? Clarifying these points would greatly aid my understanding of the concept.