[GAMEPLAY] Miss Fortune's passive - difference between buff bar and actual MS

To reproduce:

1. Take damage to disable passive.
2. Wait until passive is stacking on the buff bar.
3. Press W. The indicator on the buff bar goes to 70 MS immediately, but actual MS (at least as shown on the stats bar) does not.

This occurs every time. I tested on base and Arcade.

Please see the attached screenshot. The buff bar shows 70 MS (fully stacked), but the stats bar does not show 395 MS (325 base + 70).