Those are auto-successes as well. You don't even need to roll. you only need to roll when you want to jump higher than that. And while not specified what DC at how many additional feet, one can easily come up with a DC by looking at the DC ratings and what they mean.From the PHB:
"High Jump. When you make a high jump, you leap into the air a number of feet equal to 3 + your Strength modifier if you move at least 10 feet on foot immediately before the jump. When you make a standing high jump, you can jump only half that distance. ... In some circumstances, your DM might allow you to make a Strength (Athletics) check to jump higher than you normally can."
So 20 Str can do a Standing high jump of (3+5)/2=4 vertical feet. What would it look like to do even more than that (in some circumstances)?
The Korean game Show Physical:100 has just showed me. Enjoy.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.