if you use Angus cattle, the $indexes were made just for you.
in the most simple terms:
$W - indicates how much the cow/calf producer should make
$F - indicates how much will be made after they buy your feeders through the feedlot.
$G - indicates the value of your calves after the feedlot, when they are processed for their meat value.
$B - indicates how much will be made by the person who buys your feeder calves and owns them through $F AND $G time periods.
if you are just worried about your profits and nobody else's, maximize $W. if you want buyers to be satisfied customers and try to make a profit, find a nice mix of them all (higher being better for all 4).