This is an alternate battle speed patch from Leviathan Mist that essentially has the same purpose as the one that is already implemented in RotDS, which is HatZen's 'Even Gauge' patch. In short what this patch (and Hatzen's) does, is make it so characters are affected by the "battle speed" option in the config menu, and also fixes the overflow error when a character's speed goes over 235. Unlike HatZen's however, instead of factoring in character speed to the ATB equation, this one simply uses higher/faster values for the ATB multipliers which may lead to a slightly different battle experience overall - from my experience, early game the characters' ATB bar will be slightly faster than Even Gauge, but late-game/when the characters' speed stat is much higher it is noticeably slower overall than Even Gauge.

I'm not sure which one is "better"... I'd assume HatZen's (the one that's implemented in RotDS by default) because it factors in the character's actual speed stat, which is cool, but Leviathan Mist's feels about the same overall for all intents. So maybe try this out if this is your umpteenth time playing just to see if it feels any more to your liking or not.

Credit:
Leviathan Mist for the original patch.
Slightly altered by Gi Nattak to re-include the 1.5 multiplier.