Well, I think, there is some kind of mistake

We've Palace and Empire Mint.

Palace gives  +22 Dust on city  and Empire Mint gives  +5 Dust on city  &  +15% Dust on city .

We've  +33.2 Dust from Empire Mint  in summ.

So, let's check:

(22 + 5) + 15%

(22 + 5) * 1.15 =  31.05 (!)

Where is 33.2? Do I forget or lose something?

When I sell Empire Mint I've  +22 Dust from Palace . It's correct

Is it a bug or a feature?