The DC universe is extremely large. The distance between Earth and Maxima's galaxy is 100 trillion light years. Furthermore, the feat takes place in a universe that is much, much bigger than said mortal universe, so 100 trillion light years is quite a lowball for the radius in my opinion.
They reached it in a single panel, so I'll use three fast times to calc it:
They started out from the center of the cosmos, as the Godworld (alternately called Asgaard or Urgrund) was directly stated to be at the center, and Apokolips/New Genesis are the split-in-half remains of the Godworld.
100 trillion light years = 9.46E29 meters
Low-end: 1 minute[]
9.46e29 m / 60 s = 1.58e28 m/s
Mid-end: 30 seconds[]
9.46e29 m / 30 s = 3.15e28 m/s
High-end: 5 seconds[]
9.46e29 m / 5 s = 1.89e29 m/s
Results[]
[Accepted] Low-end: 52,703,127,041,308,024,832 or 52 quintillion times light speed
Mid-end: 1.05e20 or 105 quintillion times light speed
High-end: 6.30e20 or 630 quintillion times light speed
All ends give MFTL+ results