If you have only one building of that type, then yeah it would take 10 days. That doesn't seem strange for a story quest, honestly. They've always included researching specific technologies, scouting/acquiring specific provinces, building/producing specific productions or units, etc. Things that take time, days, and sometimes maybe even weeks depending on your resources and tech/continent map progress.oh really, its a 24 hour production
so i need 10 days for this story mission, if i have only one ShellfishFarm ...
Edit:
is this another Inno plan, to even more slow down the game ?
until they get more super creative ideas, to make another (3rd) oceanic-future-GB
i guess you found out, that i'm not happy about the last GB
even it have a over 90 % chance at lvl 60 with 14 battles (Kraken i mean)
There are "produce X 24-hour productions in Y production building" story quests at least from Industrial Age onward. Yes, I know there are smaller production buildings around that era, but the city space is also vastly smaller. Therefore you could run into the same scenario even then. You either build more if you want to progress with the quest faster, or you build less and just take your time. Ultimately the quest can be completed though.