Swing/shuffle question

5 shuffle on the 909 is the same that 55% swing on the MPC ? I dont understand why the shuffle is 50-75 on the MPC

it's how roger linn engineered it. imagine the "on grid" position of a note,then the need to move the position around that note. he visualized it as a gradient from 0 to 100%- no swing is 50% because its the center of that gradient, because you can either move it earlier (ideally it should be from 25 to 49%) or move it later (51 to 75% where 75% is practically triplet). now, we can only push notes later with the mpc swing, BUT you also have the shift timing feature, that allows you to move notes earlier.