Alma 11 is the chapter in which we learn how much each unit of Nephite money is worth, relative to other units of their money. For example, if you were living in Zarahemla at the time, you would want to know that a senum of silver is equivalent in value to a senine of gold and that either can be used to purchase a measure of barley or any other type of grain. A seon of gold is worth two senines and a shum is worth twice as much as that, and so on.
Although on the surface, U.S. money is easier to understand than Nephite currency — a $10 bill is worth twice as much as a $5 bill, and a $20 bill is worth twice as much as that, etc. — we can easily find ourselves having to do mathematical exercises with currency values when we visit other countries. For example, when I visit Central America, I keep in mind that $1 in U.S. currency is worth $2.60 in Dominica, 8 quetzals in Guatemala and 20 pesos in Mexico.