Complex sentence: About twenty "coin units" are automatically exchanged to become a single "dollar unit" (representing $1000) which becomes a single "money bag unit" (representing $10000) after eighty dollar units are gathered together.
Split into simpler sentences: About twenty "coin units" are automatically exchanged to become a single "dollar unit" (representing $1000). A certain amount of "dollar units" becomes a single "money bag unit" (representing $10000) after eighty dollar units are gathered together.