The federal poverty level is defined by the feds.

Many programs use that, or variations on like (like this 400%) - to index. So if the poverty line for a family of four is 32,150$ - then this program is available to your family of four until you make over 128,600$.

Others will say "below 200% FPL OR qualifying condition" (think newborn, pregnant, etc). So some programs are open to baseball player families, as long as the qualifying condition is there.