Gear inches is not the distance you travel per rotation. Gear inches is the equivalent diameter of a penny farthing type bike (aka no gears just one giant direct drive wheel)

so the distance you travel is 74.3" * pi or 233.42" which is .003684 miles
this is 271.4 rotations for a mile (3 minutes/mile)

20 miles at 271.4 rotations gives 5428 which is the same as your 5430