So that would be about 34.3 km/s. Earth has a 40,075 km circumference. Assuming the NnT planet is about earth sized he could jump around the world in like 20 min (about 1200 seconds) going this fast. 1step/sec would also also imply that he traveled 2470 km (he jumped 72 times) and it would have taken him a little over a minute to get there. My flight memory account is telling me that a flight from ATL to SLC is like 2,542 km. It seemed like it only took Galan a minute to get to Camelot so if Edinburgh is as far from Camelot as Atlanta is from Salt Lake City then that checks out.
That number seemed absurd at first but it could actually make sense...and that is freaking fast. That's faster than escape velocity. He could literally jump out of orbit if he was high enough.
To elaborate, I think NnT planet may be a bit bigger than ours. Because Britannia is basically England, Wales and Scotland in our real-life map, which is canon by the author's words when fan asked him about Britannia and the map we have in the databook (you can see it on the wikia). But the thing is...in real world map, the distance between Edinburgh and Lyoness is about 185km, but in the manga it's 185 miles. I'm not sure if the author intends that (which means, like I said, NnT planet is a bit bigger) or he just mistook the unit...
Camelot is in the very south of Britannia btw. Around Basingstoke in real life. That's 544km in real world map, but in NnT maybe 544 miles. Divide that by 72 steps then do a bit of geometry for triangle because Galan didn't move in straight line. He jumped up then jumped/fell down so the actual distance he moved with each step is much longer than 544/72. Of course, if we're calcwhore and want to be absolutely accurate then have to account gravity when he fell down but that's too much work. Also Mach100 is just a rough estimate. I didn't actually calculate it
And just in case if people in general made a mistake: Merlin can teleport people from Lyones to Camelot which is further than 544km/miles but that doesn't mean that's her Area of Effect (AoE). Like, she can teleport people to X place but maybe people have to be within a range for that to take place if you know what I mean. So the distance she can teleport people to is different from her AoE, which can be much much much smaller and Galan jumped out of that in less time than Mel fell to the ground from a height of...1 meter (which we can use SUVAT to calculate the time). And we still don't know her AoE