Question regarding expertise

[Norljus]

It says that for every 20 points of expertise the level of your unit improves by 1. Does that mean that a manager with anything between 41 to 59 isn't better than one with 40 ?

[13thscholar]

As a flat count to the unit that you see in the factory/store, yes that is true, with a caveat.

The 59 rank you mention still has the decimals in action, so you will upgrade or learn faster than the 41 rank.