Empire Mint bugged?

[Boomerwaffen]

My Empire Mint is providing me with aabout 35 gold (base) early game which seems like too much or what am I missing?
Other similar buildings that give about the same boost is providing me with much much less. For example Mill foundry that is also a +6 building and +15% extra industry (same stat as Empire Mint) provides 9 or 12 I think dont remember exactly right now.
Same with a few other similar buildings.

Playing Vaulters on Serious. Have only one city around turn 20. Fervent in both city and Empire. Governer only increase science.

Perhaps its normal. Cant get the numbers to match though. Perhaps I am just tired though.
Will upload picture when at computor.

[KtX2SkD]

For googlers, the bug seems to be only a display bug for the City's calculations. The final empire-level calculation checks out fine. The value shown for Empire's Mint in the City represents the sum of the following:

• +5 from Empire's Mint,
  
• +22 from Palace (if applicable),
  
• +2/+4 from Founder's Memorial (if applicable),
  
• then calculate the Empire's Mint +15% bonus on all non-percentage bonuses, including the ones stated above, and City Tiles. Add that result too.