Basically, it's pretty damn fast
Le calc[]
Sephiroth's international dimension is at Multi-galaxy size as the milky way is seen pretty small inside it and looking like the other "stars" when first zooming in, impliying that those white orbs are galaxies
so, by counting the white orbs the Supernova passed, there were 17 Galaxies the Supernova flied past
our Galaxy, is over 100,000 Light Years in size
100,000 x 17 = 700 000 Light Years
similar to my other blog related to galaxy speed feats, i will be also using Watch frame by frame in this
the Supernova started flying past those galaxies at frame 47763 and stopped at frame 47910
47763/47910 = 0.9 Seconds
sooo
0.9/700000 = 7.358474051086665e+21 m/s
or 24545227388898.043c
which is 24,545,227,388,898 times the speed of light
EDIT[]
i got the light years number wrong, it's actually 1,700,000 light years
which makes the feat 596098379444666.8c
596 098 379 444 666 times the speed of light
cool.
Results[]
Supernova flies past some galaxies = 24545227388898.043c (Massively FTL+) (OUTDATED)
Supernova flies past some galaxies = 596098379444666.8c (Massively FTL+)