What does "max. 3% of bank" stand for in Cookie Clicker?

The description for the Bakeberry seed on Cookie Clicker says that the extra 30 minutes of CpS that you can get is capped at "3% of bank". What is it referring to? 3% of the bank CpS? If that is so, it would always be capped because 30 minutes of bank CpS is smaller or equal than 30 minutes of the total CpS. That's confusing.

According to the Fandom Wiki:

Additionally, it's important to note that bakeberry harvesting rewards are capped at just 3% of your current cookies, so they should ideally only be harvested when you have loads of cookies saved up to get a bigger reward. (In order to get the full reward from all your bakeberries, you'd need to have at least 16 hours 40 minutes worth of CpS sitting there in your bank.)