It's a problem of "units" and the difference between frames/minute and minutes/frame.
"speed" is generally thought of in units/time like miles/hour and not hours/mile.
So if Car A is going 100 miles per hour and Car B is going 101 miles per hour, then Car B is going 101% of the speed of Car A and we can say Car B is gong 1% faster than Car A.
If Car A is going 100 miles per hour and Car B is going 200 miles per hour miles per hour, then Car B is going 200% of the speed of Car A and we say Car B is going 100% faster than Car A. Somewhat confusingly, 100% faster means twice the speed.
Is Car A going 100% slower than Car B? No, that would be motionless. We might say Car A is going 50% slower since it is moving half the speed of Car B, but "50% slower" isn't as intuitively meaningful as "X percent faster" is.
But if A:M v15 did 6 frames per minute and V17 does 14.5 frames per minute we can accurately say that V17, which produces frames at 240% of the speed of v15, is 140% faster than v15.