How does the 20% match work? Is it 20% of the amount of grant funding FTA apportioned, or 20% of the total combined funding level?

Match can be calculated by using the Federal Share (award) divided by the percentage of Total Project Cost minus Federal Share. A sample is as follows:
With a match of 20%, and Federal share of 80%, a $250,000 Federal grant:
$250,000 divided by 80% = $312,500
$312,500 minus $250,000 = $62,500
The 20% local share is $62,500.