Imagine if your $100 contribution to your 401K was "matched" by your employer to the tune of $1,000,000,000. This is similar to the spiritual math that Abram sees in his spiritual account: He believes. Then God credits him with RIGHTEOUSNESS. God makes Abram spiritually acceptable before him.
Here's the kicker: We should care about this because WE MUST DO THE SAME as Abram, and GOD MUST DO THE SAME for us in grace. Listen. Better yet: watch this one here: