Movement speed modifiers calculated incorrectly

The movement speed modifier in the character sheet is incorrect. It appears the hidden implicit 4% movement speed penalty of chest pieces is being applied as a less modifier as well as a reduced modifiers.

Ex. As 10% move speed boots would be calculated as

0(base) - 4%(chest penalty) + 10%(boots) × (100- 4)%(chest penalty again)

This results in a modifier of 5.6% rather than the expected 6%.

This may just be a display bug with the character sheet and not reflect actual character speed. Further testing required.

THAT'S why I see that movement speed penalty? Because my character is wearing armor? Why does it exist?

It's a holdover from the days in poe1 where racing was a big thing. The idea was players could get an edge over others by forgoing some defenses in exchange for some speed. Armour weighs you down, you know?

can confirm, my ES armour gives me -3% on sheet while not wearing boots. And +26.1% while wearing 30% boots.

Was expecting 27%.

Also temporal chains on maps is shown as 7%, but it seems to be a lot more.