To summarize, Merlin attempts to teleport Galan away from everyone else. Galan sees her spell beginning, and promptly jumps out of her range before Meliodas can hit the ground, then jumps back right after the spell is done.
The first thing we need to figure out is Merlin's range. This one is actually pretty easy, since a minimum is stated in the manga.
It's 270 km, since Merlin is capable of teleporting people from Edinburg to Liones. This isn't a maximum, of course, but it'll serve our purposes.
So now we need the timeframe. We know Galan escaped her range in at most the time it took Meliodas to hit the ground. We also know Meliodas is 1.52 m tall, and that he's around 167 px tall here while hanging about 296 px off the ground. This means the drop is 2.69 m, which gives us all the variables we need for the timeframe and, from there, the speed.
t = √(2*h/g)
- h = 2.69 m
- g = 9.8 m/s^2
√(2*2.69/9.8) = 0.74 s
v = d/t
- d = 270,000 m
- t = 0.74 s
270,000/0.74 = 365,000 m/s
Result
- Galan Jumps Quickly - Mach 1070